From its launch in 2018 to mid 2025, EQUS published over 500 papers detailing scientific discoveries in fields as diverse as quantum information to new medical imaging technologies.
Access the full list of EQUS papers below.
2025
D. Singh; G. Muraleedharan; B. Fu; C-M. Cheng; N. R. Newton; P. P. Rohde; G. K. Brennen
Proof-of-work consensus by quantum sampling Journal Article
In: Quantum Sci. Technol., vol. 10, no. 2, 2025, ISSN: 2058-9565.
Abstract | Links | BibTeX | Tags:
@article{Singh2025,
title = {Proof-of-work consensus by quantum sampling},
author = {D. Singh and G. Muraleedharan and B. Fu and C-M. Cheng and N. R. Newton and P. P. Rohde and G. K. Brennen},
doi = {10.1088/2058-9565/adae2b},
issn = {2058-9565},
year = {2025},
date = {2025-04-01},
urldate = {2025-04-01},
journal = {Quantum Sci. Technol.},
volume = {10},
number = {2},
publisher = {IOP Publishing},
abstract = {<jats:title>Abstract</jats:title>
<jats:p>Since its advent in 2011, boson sampling has been a preferred candidate for demonstrating quantum advantage because of its simplicity and near-term requirements compared to other quantum algorithms. We propose to use a variant, called coarse-grained boson-sampling (CGBS), as a quantum proof-of-work (PoW) scheme for blockchain consensus. The miners perform boson sampling using input states that depend on the current block information and commit their samples to the network. Afterwards, CGBS strategies are determined which can be used to both validate samples and reward successful miners. By combining rewards for miners committing honest samples together with penalties for miners committing dishonest samples, a Nash equilibrium is found that incentivises honest miners. We provide numerical evidence that these validation tests are hard to spoof classically without knowing the binning scheme ahead of time and show the robustness of our protocol to small partial distinguishability of photons. The scheme works for both Fock state boson sampling and Gaussian boson sampling and provides dramatic speedup and energy savings relative to computation by classical hardware.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title>
<jats:p>Since its advent in 2011, boson sampling has been a preferred candidate for demonstrating quantum advantage because of its simplicity and near-term requirements compared to other quantum algorithms. We propose to use a variant, called coarse-grained boson-sampling (CGBS), as a quantum proof-of-work (PoW) scheme for blockchain consensus. The miners perform boson sampling using input states that depend on the current block information and commit their samples to the network. Afterwards, CGBS strategies are determined which can be used to both validate samples and reward successful miners. By combining rewards for miners committing honest samples together with penalties for miners committing dishonest samples, a Nash equilibrium is found that incentivises honest miners. We provide numerical evidence that these validation tests are hard to spoof classically without knowing the binning scheme ahead of time and show the robustness of our protocol to small partial distinguishability of photons. The scheme works for both Fock state boson sampling and Gaussian boson sampling and provides dramatic speedup and energy savings relative to computation by classical hardware.</jats:p>
<jats:p>Since its advent in 2011, boson sampling has been a preferred candidate for demonstrating quantum advantage because of its simplicity and near-term requirements compared to other quantum algorithms. We propose to use a variant, called coarse-grained boson-sampling (CGBS), as a quantum proof-of-work (PoW) scheme for blockchain consensus. The miners perform boson sampling using input states that depend on the current block information and commit their samples to the network. Afterwards, CGBS strategies are determined which can be used to both validate samples and reward successful miners. By combining rewards for miners committing honest samples together with penalties for miners committing dishonest samples, a Nash equilibrium is found that incentivises honest miners. We provide numerical evidence that these validation tests are hard to spoof classically without knowing the binning scheme ahead of time and show the robustness of our protocol to small partial distinguishability of photons. The scheme works for both Fock state boson sampling and Gaussian boson sampling and provides dramatic speedup and energy savings relative to computation by classical hardware.</jats:p>
L. Lootens; C. Delcamp; D. J. Williamson; F. Verstraete
Low-Depth Unitary Quantum Circuits for Dualities in One-Dimensional Quantum Lattice Models Journal Article
In: Phys. Rev. Lett., vol. 134, no. 13, 2025, ISSN: 1079-7114.
Abstract | Links | BibTeX | Tags:
@article{Lootens2025,
title = {Low-Depth Unitary Quantum Circuits for Dualities in One-Dimensional Quantum Lattice Models},
author = {L. Lootens and C. Delcamp and D. J. Williamson and F. Verstraete},
doi = {10.1103/physrevlett.134.130403},
issn = {1079-7114},
year = {2025},
date = {2025-04-00},
urldate = {2025-04-00},
journal = {Phys. Rev. Lett.},
volume = {134},
number = {13},
publisher = {American Physical Society (APS)},
abstract = {<jats:p>A systematic approach to dualities in symmetric <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mo stretchy="false">(</a:mo><a:mn>1</a:mn><a:mo>+</a:mo><a:mn>1</a:mn><a:mo stretchy="false">)</a:mo><a:mi mathvariant="normal">d</a:mi></a:mrow></a:math> quantum lattice models has recently been proposed in terms of module categories over the symmetry fusion categories. By characterizing the nontrivial way in which dualities intertwine closed boundary conditions and charge sectors, these can be implemented by unitary matrix product operators. In this Letter, we explain how to turn such duality operators into unitary linear depth quantum circuits via the introduction of ancillary degrees of freedom that keep track of the various sectors. The linear depth is consistent with the fact that these dualities change the phase of the states on which they act. When supplemented with measurements, we show that dualities with respect to symmetries encoded into nilpotent fusion categories can be realized in constant depth. The resulting circuits can for instance be used to efficiently prepare short- and long-range entangled states or map between different gapped boundaries of <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mrow><f:mo stretchy="false">(</f:mo><f:mn>2</f:mn><f:mo>+</f:mo><f:mn>1</f:mn><f:mo stretchy="false">)</f:mo><f:mi mathvariant="normal">d</f:mi></f:mrow></f:math> topological models.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>A systematic approach to dualities in symmetric <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mo stretchy="false">(</a:mo><a:mn>1</a:mn><a:mo>+</a:mo><a:mn>1</a:mn><a:mo stretchy="false">)</a:mo><a:mi mathvariant="normal">d</a:mi></a:mrow></a:math> quantum lattice models has recently been proposed in terms of module categories over the symmetry fusion categories. By characterizing the nontrivial way in which dualities intertwine closed boundary conditions and charge sectors, these can be implemented by unitary matrix product operators. In this Letter, we explain how to turn such duality operators into unitary linear depth quantum circuits via the introduction of ancillary degrees of freedom that keep track of the various sectors. The linear depth is consistent with the fact that these dualities change the phase of the states on which they act. When supplemented with measurements, we show that dualities with respect to symmetries encoded into nilpotent fusion categories can be realized in constant depth. The resulting circuits can for instance be used to efficiently prepare short- and long-range entangled states or map between different gapped boundaries of <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mrow><f:mo stretchy="false">(</f:mo><f:mn>2</f:mn><f:mo>+</f:mo><f:mn>1</f:mn><f:mo stretchy="false">)</f:mo><f:mi mathvariant="normal">d</f:mi></f:mrow></f:math> topological models.</jats:p>
G. Tobar; I. Pikovski; M. E. Tobar
Detecting kHz gravitons from a neutron star merger with a multi-mode resonant mass detector Journal Article
In: Class. Quantum Grav., vol. 42, no. 5, 2025, ISSN: 1361-6382.
Abstract | Links | BibTeX | Tags:
@article{Tobar2025,
title = {Detecting kHz gravitons from a neutron star merger with a multi-mode resonant mass detector},
author = {G. Tobar and I. Pikovski and M. E. Tobar},
doi = {10.1088/1361-6382/adae4a},
issn = {1361-6382},
year = {2025},
date = {2025-03-07},
urldate = {2025-03-07},
journal = {Class. Quantum Grav.},
volume = {42},
number = {5},
publisher = {IOP Publishing},
abstract = {<jats:title>Abstract</jats:title>
<jats:p>We propose a multi-mode bar consisting of mass elements of decreasing size for the implementation of a gravitational version of the photo-electric effect through the stimulated absorption of up to kHz gravitons from a binary neutron star merger and post-merger. We find that the multi-mode detector has normal modes that retain the coupling strength to the gravitational wave of the largest mass-element, while only having an effective mass comparable to the mass of the smallest element. This allows the normal modes to have graviton absorption rates due to the tonne-scale largest mass, while the single graviton absorption process in the normal mode could be resolved through energy measurements of a mass-element in-principle smaller than pico-gram scale. We argue the feasibility of directly counting gravito-phonons in the bar through energy measurements of the end mass. This improves the transduction of the single-graviton signal, enhancing the feasibility of detecting single gravitons.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title>
<jats:p>We propose a multi-mode bar consisting of mass elements of decreasing size for the implementation of a gravitational version of the photo-electric effect through the stimulated absorption of up to kHz gravitons from a binary neutron star merger and post-merger. We find that the multi-mode detector has normal modes that retain the coupling strength to the gravitational wave of the largest mass-element, while only having an effective mass comparable to the mass of the smallest element. This allows the normal modes to have graviton absorption rates due to the tonne-scale largest mass, while the single graviton absorption process in the normal mode could be resolved through energy measurements of a mass-element in-principle smaller than pico-gram scale. We argue the feasibility of directly counting gravito-phonons in the bar through energy measurements of the end mass. This improves the transduction of the single-graviton signal, enhancing the feasibility of detecting single gravitons.</jats:p>
<jats:p>We propose a multi-mode bar consisting of mass elements of decreasing size for the implementation of a gravitational version of the photo-electric effect through the stimulated absorption of up to kHz gravitons from a binary neutron star merger and post-merger. We find that the multi-mode detector has normal modes that retain the coupling strength to the gravitational wave of the largest mass-element, while only having an effective mass comparable to the mass of the smallest element. This allows the normal modes to have graviton absorption rates due to the tonne-scale largest mass, while the single graviton absorption process in the normal mode could be resolved through energy measurements of a mass-element in-principle smaller than pico-gram scale. We argue the feasibility of directly counting gravito-phonons in the bar through energy measurements of the end mass. This improves the transduction of the single-graviton signal, enhancing the feasibility of detecting single gravitons.</jats:p>
C. Goodman; M. Guzzetti; C. Hanretty; L. J. Rosenberg; G. Rybka; J. Sinnis; D. Zhang; J. Clarke; I. Siddiqi; A. S. Chou; M. Hollister; S. Knirck; A. Sonnenschein; T. J. Caligiure; J. R. Gleason; A. T. Hipp; P. Sikivie; M. E. Solano; N. S. Sullivan; D. B. Tanner; R. Khatiwada; G. Carosi; C. Cisneros; N. Du; N. Robertson; N. Woollett; L. D. Duffy; C. Boutan; T. Braine; E. Lentz; N. S. Oblath; M. S. Taubman; E. J. Daw; C. Mostyn; M. G. Perry; C. Bartram; T. A. Dyson; S. Ruppert; M. O. Withers; C. L. Kuo; B. T. McAllister; J. H. Buckley; C. Gaikwad; J. Hoffman; K. W. Murch; M. Goryachev; E. Hartman; A. Quiskamp; M. E. Tobar
ADMX Axion Dark Matter Bounds around $3.3text text mathrmensuremathmumathrmeV$ with Dine-Fischler-Srednicki-Zhitnitsky Discovery Ability Journal Article
In: Phys. Rev. Lett., vol. 134, iss. 11, pp. 111002, 2025.
@article{PhysRevLett.134.111002,
title = {ADMX Axion Dark Matter Bounds around $3.3text text mathrmensuremathmumathrmeV$ with Dine-Fischler-Srednicki-Zhitnitsky Discovery Ability},
author = {C. Goodman and M. Guzzetti and C. Hanretty and L. J. Rosenberg and G. Rybka and J. Sinnis and D. Zhang and J. Clarke and I. Siddiqi and A. S. Chou and M. Hollister and S. Knirck and A. Sonnenschein and T. J. Caligiure and J. R. Gleason and A. T. Hipp and P. Sikivie and M. E. Solano and N. S. Sullivan and D. B. Tanner and R. Khatiwada and G. Carosi and C. Cisneros and N. Du and N. Robertson and N. Woollett and L. D. Duffy and C. Boutan and T. Braine and E. Lentz and N. S. Oblath and M. S. Taubman and E. J. Daw and C. Mostyn and M. G. Perry and C. Bartram and T. A. Dyson and S. Ruppert and M. O. Withers and C. L. Kuo and B. T. McAllister and J. H. Buckley and C. Gaikwad and J. Hoffman and K. W. Murch and M. Goryachev and E. Hartman and A. Quiskamp and M. E. Tobar},
url = {https://link.aps.org/doi/10.1103/PhysRevLett.134.111002},
doi = {10.1103/PhysRevLett.134.111002},
year = {2025},
date = {2025-03-01},
urldate = {2025-03-01},
journal = {Phys. Rev. Lett.},
volume = {134},
issue = {11},
pages = {111002},
publisher = {American Physical Society},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
M. E. S. Morales; P. C. S. Costa; G. Pantaleoni; D. Burgarth; Y. R. Sanders; D. W. Berry
Selection and Improvement of Product Formulae for Best Performance of Quantum Simulation Journal Article
In: vol. 25, no. 1, pp. 1–35, 2025, ISSN: 1533-7146.
Abstract | Links | BibTeX | Tags:
@article{Morales2025,
title = {Selection and Improvement of Product Formulae for Best Performance of Quantum Simulation},
author = {M. E. S. Morales and P. C. S. Costa and G. Pantaleoni and D. Burgarth and Y. R. Sanders and D. W. Berry},
doi = {10.2478/qic-2025-0001},
issn = {1533-7146},
year = {2025},
date = {2025-03-01},
urldate = {2025-03-01},
volume = {25},
number = {1},
pages = {1--35},
publisher = {Walter de Gruyter GmbH},
abstract = {<jats:title>Abstract</jats:title>
<jats:p>Quantum algorithms for simulation of Hamiltonian evolution are often based on product formulae. The fractal methods give a systematic way to find arbitrarily high-order product formulae, but result in a large number of exponentials. On the other hand, product formulae with fewer exponentials can be found by numerical solution of simultaneous non-linear equations. It is also possible to reduce the cost of long-time simulations by processing, where a kernel is repeated and a processor need only be applied at the beginning and end of the simulation. In this work, we found thousands of new product formulae, and numerically tested these formulae, together with many formulae from prior literature. We provide methods to fairly compare product formulae of different lengths and different orders. For the case of 8th order, we have found new product formulae with exceptional performance, about two orders of magnitude better accuracy than prior work, both in the processed and non-processed cases. The processed product formula provides the best performance due to being shorter than the non-processed product formula. It outperforms all other tested product formulae over a range of many orders of magnitude in system parameters <jats:italic>T</jats:italic> (time) and <jats:italic>ε</jats:italic> (allowable error). That includes reasonable combinations of parameters to be used in quantum algorithms, where the size of the simulation is large enough to be classically intractable, but not so large it takes an impractically long time on a quantum computer.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
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<jats:title>Abstract</jats:title>
<jats:p>Quantum algorithms for simulation of Hamiltonian evolution are often based on product formulae. The fractal methods give a systematic way to find arbitrarily high-order product formulae, but result in a large number of exponentials. On the other hand, product formulae with fewer exponentials can be found by numerical solution of simultaneous non-linear equations. It is also possible to reduce the cost of long-time simulations by processing, where a kernel is repeated and a processor need only be applied at the beginning and end of the simulation. In this work, we found thousands of new product formulae, and numerically tested these formulae, together with many formulae from prior literature. We provide methods to fairly compare product formulae of different lengths and different orders. For the case of 8th order, we have found new product formulae with exceptional performance, about two orders of magnitude better accuracy than prior work, both in the processed and non-processed cases. The processed product formula provides the best performance due to being shorter than the non-processed product formula. It outperforms all other tested product formulae over a range of many orders of magnitude in system parameters <jats:italic>T</jats:italic> (time) and <jats:italic>ε</jats:italic> (allowable error). That includes reasonable combinations of parameters to be used in quantum algorithms, where the size of the simulation is large enough to be classically intractable, but not so large it takes an impractically long time on a quantum computer.</jats:p>
<jats:p>Quantum algorithms for simulation of Hamiltonian evolution are often based on product formulae. The fractal methods give a systematic way to find arbitrarily high-order product formulae, but result in a large number of exponentials. On the other hand, product formulae with fewer exponentials can be found by numerical solution of simultaneous non-linear equations. It is also possible to reduce the cost of long-time simulations by processing, where a kernel is repeated and a processor need only be applied at the beginning and end of the simulation. In this work, we found thousands of new product formulae, and numerically tested these formulae, together with many formulae from prior literature. We provide methods to fairly compare product formulae of different lengths and different orders. For the case of 8th order, we have found new product formulae with exceptional performance, about two orders of magnitude better accuracy than prior work, both in the processed and non-processed cases. The processed product formula provides the best performance due to being shorter than the non-processed product formula. It outperforms all other tested product formulae over a range of many orders of magnitude in system parameters <jats:italic>T</jats:italic> (time) and <jats:italic>ε</jats:italic> (allowable error). That includes reasonable combinations of parameters to be used in quantum algorithms, where the size of the simulation is large enough to be classically intractable, but not so large it takes an impractically long time on a quantum computer.</jats:p>
E. T. Hockings
QuantumACES.jl: design noise characterisation experiments for quantum computers Journal Article
In: JOSS, vol. 10, no. 107, 2025, ISSN: 2475-9066.
@article{Hockings2025,
title = {QuantumACES.jl: design noise characterisation experiments for quantum computers},
author = {E. T. Hockings},
doi = {10.21105/joss.07707},
issn = {2475-9066},
year = {2025},
date = {2025-03-00},
urldate = {2025-03-00},
journal = {JOSS},
volume = {10},
number = {107},
publisher = {The Open Journal},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
O. Hart; D. T. Stephen; D. J. Williamson; M. Foss-Feig; R. Nandkishore
Playing Nonlocal Games across a Topological Phase Transition on a Quantum Computer Journal Article
In: Phys. Rev. Lett., vol. 134, no. 13, 2025, ISSN: 1079-7114.
@article{Hart2025,
title = {Playing Nonlocal Games across a Topological Phase Transition on a Quantum Computer},
author = {O. Hart and D. T. Stephen and D. J. Williamson and M. Foss-Feig and R. Nandkishore},
doi = {10.1103/physrevlett.134.130602},
issn = {1079-7114},
year = {2025},
date = {2025-03-00},
urldate = {2025-03-00},
journal = {Phys. Rev. Lett.},
volume = {134},
number = {13},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
B. W. Walshe; B. Q. Baragiola; H. Ferretti; J. Gefaell; M. Vasmer; R. Weil; T. Matsuura; T. Jaeken; G. Pantaleoni; Z. Han; T. Hillmann; N. C. Menicucci; I. Tzitrin; R. N. Alexander
Linear-Optical Quantum Computation with Arbitrary Error-Correcting Codes Journal Article
In: Phys. Rev. Lett., vol. 134, no. 10, 2025, ISSN: 1079-7114.
@article{Walshe2025,
title = {Linear-Optical Quantum Computation with Arbitrary Error-Correcting Codes},
author = {B. W. Walshe and B. Q. Baragiola and H. Ferretti and J. Gefaell and M. Vasmer and R. Weil and T. Matsuura and T. Jaeken and G. Pantaleoni and Z. Han and T. Hillmann and N. C. Menicucci and I. Tzitrin and R. N. Alexander},
doi = {10.1103/physrevlett.134.100602},
issn = {1079-7114},
year = {2025},
date = {2025-03-00},
urldate = {2025-03-00},
journal = {Phys. Rev. Lett.},
volume = {134},
number = {10},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
L. G. Bishop; F. Costa; T. C. Ralph
Quantum state tomography on closed timelike curves using weak measurements Journal Article
In: Class. Quantum Grav., vol. 42, no. 4, 2025, ISSN: 1361-6382.
Abstract | Links | BibTeX | Tags:
@article{Bishop2025,
title = {Quantum state tomography on closed timelike curves using weak measurements},
author = {L. G. Bishop and F. Costa and T. C. Ralph},
doi = {10.1088/1361-6382/ada90b},
issn = {1361-6382},
year = {2025},
date = {2025-02-21},
urldate = {2025-02-21},
journal = {Class. Quantum Grav.},
volume = {42},
number = {4},
publisher = {IOP Publishing},
abstract = {<jats:title>Abstract</jats:title>
<jats:p>Any given prescription of quantum time travel necessarily endows a Hilbert space to the chronology-violating (CV) system on the closed timelike curve (CTC). However, under the two foremost models, Deutsch’s prescription (D-CTCs) and postselected teleportation (P-CTCs), the CV system is treated very differently: D-CTCs assign a definite form to the state on this system, while P-CTCs do not. To further explore this distinction, we present a methodology by which an operational notion of state may be assigned to their respective CV systems. This is accomplished via a conjunction of state tomography and weak measurements, with the latter being essential in leaving any notions of self-consistency intact. With this technique, we are able to verify the predictions of D-CTCs and, perhaps more significantly, operationally assign a state to the system on the P-CTC. We show that, for any given combination of chronology-respecting input and unitary interaction, it is always possible to recover the unique state on the P-CTC, and we provide a few specific examples in the context of select archetypal temporal paradoxes. We also demonstrate how this state may be derived from analysis of the P-CTC prescription itself, and we explore how it compares to its counterpart in the CV state predicted by D-CTCs.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title>
<jats:p>Any given prescription of quantum time travel necessarily endows a Hilbert space to the chronology-violating (CV) system on the closed timelike curve (CTC). However, under the two foremost models, Deutsch’s prescription (D-CTCs) and postselected teleportation (P-CTCs), the CV system is treated very differently: D-CTCs assign a definite form to the state on this system, while P-CTCs do not. To further explore this distinction, we present a methodology by which an operational notion of state may be assigned to their respective CV systems. This is accomplished via a conjunction of state tomography and weak measurements, with the latter being essential in leaving any notions of self-consistency intact. With this technique, we are able to verify the predictions of D-CTCs and, perhaps more significantly, operationally assign a state to the system on the P-CTC. We show that, for any given combination of chronology-respecting input and unitary interaction, it is always possible to recover the unique state on the P-CTC, and we provide a few specific examples in the context of select archetypal temporal paradoxes. We also demonstrate how this state may be derived from analysis of the P-CTC prescription itself, and we explore how it compares to its counterpart in the CV state predicted by D-CTCs.</jats:p>
<jats:p>Any given prescription of quantum time travel necessarily endows a Hilbert space to the chronology-violating (CV) system on the closed timelike curve (CTC). However, under the two foremost models, Deutsch’s prescription (D-CTCs) and postselected teleportation (P-CTCs), the CV system is treated very differently: D-CTCs assign a definite form to the state on this system, while P-CTCs do not. To further explore this distinction, we present a methodology by which an operational notion of state may be assigned to their respective CV systems. This is accomplished via a conjunction of state tomography and weak measurements, with the latter being essential in leaving any notions of self-consistency intact. With this technique, we are able to verify the predictions of D-CTCs and, perhaps more significantly, operationally assign a state to the system on the P-CTC. We show that, for any given combination of chronology-respecting input and unitary interaction, it is always possible to recover the unique state on the P-CTC, and we provide a few specific examples in the context of select archetypal temporal paradoxes. We also demonstrate how this state may be derived from analysis of the P-CTC prescription itself, and we explore how it compares to its counterpart in the CV state predicted by D-CTCs.</jats:p>
J. Foo; M. Zych
Superpositions of thermalisations in relativistic quantum field theory Journal Article
In: Quantum, vol. 9, 2025, ISSN: 2521-327X.
Abstract | Links | BibTeX | Tags:
@article{Foo2025,
title = {Superpositions of thermalisations in relativistic quantum field theory},
author = {J. Foo and M. Zych},
doi = {10.22331/q-2025-02-11-1629},
issn = {2521-327X},
year = {2025},
date = {2025-02-11},
urldate = {2025-02-11},
journal = {Quantum},
volume = {9},
publisher = {Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften},
abstract = {<jats:p>Recent results in relativistic quantum information and quantum thermodynamics have independently shown that in the quantum regime, a system may fail to thermalise when subject to quantum-controlled application of the same, single thermalisation channel. For example, an accelerating system with fixed proper acceleration is known to thermalise to an acceleration-dependent temperature, known as the Unruh temperature. However, the same system in a superposition of spatially translated trajectories that share the same proper acceleration fails to thermalise. Here, we provide an explanation of these results using the framework of quantum field theory in relativistic noninertial reference frames. We show how a probe that accelerates in a superposition of spatial translations interacts with incommensurate sets of field modes. In special cases where the modes are orthogonal (for example, when the Rindler wedges are translated in a direction orthogonal to the plane of motion), thermalisation does indeed result, corroborating the here provided explanation. We then discuss how this description relates to an information-theoretic approach aimed at studying quantum aspects of temperature through quantum-controlled thermalisations. The present work draws a connection between research in quantum information, relativistic physics, and quantum thermodynamics, in particular showing that relativistic quantum effects can provide a natural realisation of quantum thermodynamical scenarios.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Recent results in relativistic quantum information and quantum thermodynamics have independently shown that in the quantum regime, a system may fail to thermalise when subject to quantum-controlled application of the same, single thermalisation channel. For example, an accelerating system with fixed proper acceleration is known to thermalise to an acceleration-dependent temperature, known as the Unruh temperature. However, the same system in a superposition of spatially translated trajectories that share the same proper acceleration fails to thermalise. Here, we provide an explanation of these results using the framework of quantum field theory in relativistic noninertial reference frames. We show how a probe that accelerates in a superposition of spatial translations interacts with incommensurate sets of field modes. In special cases where the modes are orthogonal (for example, when the Rindler wedges are translated in a direction orthogonal to the plane of motion), thermalisation does indeed result, corroborating the here provided explanation. We then discuss how this description relates to an information-theoretic approach aimed at studying quantum aspects of temperature through quantum-controlled thermalisations. The present work draws a connection between research in quantum information, relativistic physics, and quantum thermodynamics, in particular showing that relativistic quantum effects can provide a natural realisation of quantum thermodynamical scenarios.</jats:p>
F. Costa; J. Barrett; S. Shrapnel
A de Finetti theorem for quantum causal structures Journal Article
In: Quantum, vol. 9, 2025, ISSN: 2521-327X.
Abstract | Links | BibTeX | Tags:
@article{Costa2025,
title = {A de Finetti theorem for quantum causal structures},
author = {F. Costa and J. Barrett and S. Shrapnel},
doi = {10.22331/q-2025-02-11-1628},
issn = {2521-327X},
year = {2025},
date = {2025-02-11},
urldate = {2025-02-11},
journal = {Quantum},
volume = {9},
publisher = {Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften},
abstract = {<jats:p>What does it mean for a causal structure to be `unknown'? Can we even talk about `repetitions' of an experiment without prior knowledge of causal relations? And under what conditions can we say that a set of processes with arbitrary, possibly indefinite, causal structure are independent and identically distributed? Similar questions for classical probabilities, quantum states, and quantum channels are beautifully answered by so-called "de Finetti theorems", which connect a simple and easy-to-justify condition – symmetry under exchange – with a very particular multipartite structure: a mixture of identical states/channels. Here we extend the result to processes with arbitrary causal structure, including indefinite causal order and multi-time, non-Markovian processes applicable to noisy quantum devices. The result also implies a new class of de Finetti theorems for quantum states subject to a large class of linear constraints, which can be of independent interest.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>What does it mean for a causal structure to be `unknown'? Can we even talk about `repetitions' of an experiment without prior knowledge of causal relations? And under what conditions can we say that a set of processes with arbitrary, possibly indefinite, causal structure are independent and identically distributed? Similar questions for classical probabilities, quantum states, and quantum channels are beautifully answered by so-called "de Finetti theorems", which connect a simple and easy-to-justify condition – symmetry under exchange – with a very particular multipartite structure: a mixture of identical states/channels. Here we extend the result to processes with arbitrary causal structure, including indefinite causal order and multi-time, non-Markovian processes applicable to noisy quantum devices. The result also implies a new class of de Finetti theorems for quantum states subject to a large class of linear constraints, which can be of independent interest.</jats:p>
T. Kaur; D. Peace; J. Romero
On-chip high-dimensional entangled photon sources Journal Article
In: J. Opt., vol. 27, no. 2, 2025, ISSN: 2040-8986.
Abstract | Links | BibTeX | Tags:
@article{Kaur2025,
title = {On-chip high-dimensional entangled photon sources},
author = {T. Kaur and D. Peace and J. Romero},
doi = {10.1088/2040-8986/ada0c5},
issn = {2040-8986},
year = {2025},
date = {2025-02-01},
urldate = {2025-02-01},
journal = {J. Opt.},
volume = {27},
number = {2},
publisher = {IOP Publishing},
abstract = {<jats:title>Abstract</jats:title>
<jats:p>High-dimensional quantum entanglement is an important resource for emerging quantum technologies such as quantum communication and quantum computation. The scalability of metres-long experimental setups limits high-dimensional entanglement in bulk optics. Advancements in quantum technology hinge on reproducible, and reconfigurable quantum devices—including photon sources, which are challenging to achieve in a scalable manner using bulk optics. Advances in nanotechnology and CMOS-compatible integration techniques have enabled the generation of entangled photons on millimeter-scale chips, significantly enhancing scalability, stability, replicability, and miniaturization for real-world quantum applications. In recent years we have seen several chip-scale demonstrations with different discrete degrees of freedom including path, frequency-bin, time-bin, and transverse modes, on many material platforms. A complete quantum photonic integrated circuit requires the generation, manipulation, and detection of quantum states, involving various active and passive quantum photonic components which further increase the degree of complexity. Here, we focus on the high-dimensional versions of qubits—qudits—and review the nonlinear optical processes that facilitate on-chip high-dimensional entangled photon sources, and the currently used material platforms. We discuss a range of current implementations of on-chip high-dimensional entangled photon sources and demonstrated applications. We comment on the current challenges due to the limitations of individual material platforms and present future opportunities in hybrid and heterogeneous integration strategies for the next generation of integrated quantum photonic chips.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title>
<jats:p>High-dimensional quantum entanglement is an important resource for emerging quantum technologies such as quantum communication and quantum computation. The scalability of metres-long experimental setups limits high-dimensional entanglement in bulk optics. Advancements in quantum technology hinge on reproducible, and reconfigurable quantum devices—including photon sources, which are challenging to achieve in a scalable manner using bulk optics. Advances in nanotechnology and CMOS-compatible integration techniques have enabled the generation of entangled photons on millimeter-scale chips, significantly enhancing scalability, stability, replicability, and miniaturization for real-world quantum applications. In recent years we have seen several chip-scale demonstrations with different discrete degrees of freedom including path, frequency-bin, time-bin, and transverse modes, on many material platforms. A complete quantum photonic integrated circuit requires the generation, manipulation, and detection of quantum states, involving various active and passive quantum photonic components which further increase the degree of complexity. Here, we focus on the high-dimensional versions of qubits—qudits—and review the nonlinear optical processes that facilitate on-chip high-dimensional entangled photon sources, and the currently used material platforms. We discuss a range of current implementations of on-chip high-dimensional entangled photon sources and demonstrated applications. We comment on the current challenges due to the limitations of individual material platforms and present future opportunities in hybrid and heterogeneous integration strategies for the next generation of integrated quantum photonic chips.</jats:p>
<jats:p>High-dimensional quantum entanglement is an important resource for emerging quantum technologies such as quantum communication and quantum computation. The scalability of metres-long experimental setups limits high-dimensional entanglement in bulk optics. Advancements in quantum technology hinge on reproducible, and reconfigurable quantum devices—including photon sources, which are challenging to achieve in a scalable manner using bulk optics. Advances in nanotechnology and CMOS-compatible integration techniques have enabled the generation of entangled photons on millimeter-scale chips, significantly enhancing scalability, stability, replicability, and miniaturization for real-world quantum applications. In recent years we have seen several chip-scale demonstrations with different discrete degrees of freedom including path, frequency-bin, time-bin, and transverse modes, on many material platforms. A complete quantum photonic integrated circuit requires the generation, manipulation, and detection of quantum states, involving various active and passive quantum photonic components which further increase the degree of complexity. Here, we focus on the high-dimensional versions of qubits—qudits—and review the nonlinear optical processes that facilitate on-chip high-dimensional entangled photon sources, and the currently used material platforms. We discuss a range of current implementations of on-chip high-dimensional entangled photon sources and demonstrated applications. We comment on the current challenges due to the limitations of individual material platforms and present future opportunities in hybrid and heterogeneous integration strategies for the next generation of integrated quantum photonic chips.</jats:p>
S. Simjanovski; G. Gauthier; H. Rubinsztein-Dunlop; M. T. Reeves; T. W. Neely
Shear-induced decaying turbulence in Bose-Einstein condensates Journal Article
In: Phys. Rev. A, vol. 111, no. 2, 2025, ISSN: 2469-9934.
@article{Simjanovski2025,
title = {Shear-induced decaying turbulence in Bose-Einstein condensates},
author = {S. Simjanovski and G. Gauthier and H. Rubinsztein-Dunlop and M. T. Reeves and T. W. Neely},
doi = {10.1103/physreva.111.023314},
issn = {2469-9934},
year = {2025},
date = {2025-02-00},
journal = {Phys. Rev. A},
volume = {111},
number = {2},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
M. T. Hatzon; G. R. Flower; M. Goryachev; J. Bourhill; M. E. Tobar
Sharp electromagnetically induced absorption via balanced interferometric excitation in a microwave resonator Journal Article
In: Phys. Rev. Applied, vol. 23, no. 2, 2025, ISSN: 2331-7019.
@article{Hatzon2025,
title = {Sharp electromagnetically induced absorption via balanced interferometric excitation in a microwave resonator},
author = {M. T. Hatzon and G. R. Flower and M. Goryachev and J. Bourhill and M. E. Tobar},
doi = {10.1103/physrevapplied.23.024058},
issn = {2331-7019},
year = {2025},
date = {2025-02-00},
urldate = {2025-02-00},
journal = {Phys. Rev. Applied},
volume = {23},
number = {2},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
E. T. Hockings; A. C. Doherty; R. Harper
Scalable Noise Characterization of Syndrome-Extraction Circuits with Averaged Circuit Eigenvalue Sampling Journal Article
In: PRX Quantum, vol. 6, no. 1, 2025, ISSN: 2691-3399.
Abstract | Links | BibTeX | Tags:
@article{Hockings2025b,
title = {Scalable Noise Characterization of Syndrome-Extraction Circuits with Averaged Circuit Eigenvalue Sampling},
author = {E. T. Hockings and A. C. Doherty and R. Harper},
doi = {10.1103/prxquantum.6.010334},
issn = {2691-3399},
year = {2025},
date = {2025-02-00},
urldate = {2025-02-00},
journal = {PRX Quantum},
volume = {6},
number = {1},
publisher = {American Physical Society (APS)},
abstract = {<jats:p>Characterizing the performance of noisy quantum circuits is central to the production of prototype quantum computers and can enable improved quantum error correction that exploits noise biases identified in a quantum device. We develop a scalable noise-characterization protocol suited to characterizing the syndrome-extraction circuits of quantum error-correcting codes, a key component of fault-tolerant architectures. Our protocol builds upon averaged circuit eigenvalue sampling (ACES), a framework for noise-characterization experiments that simultaneously estimates the Pauli-error probabilities of all gates in a Clifford circuit and captures averaged spatial correlations between gates implemented simultaneously in the layers of the circuit. By rigorously analyzing the performance of noise-characterization experiments in the ACES framework, we derive a figure of merit for their expected performance, allowing us to optimize their experimental design and improve the precision to which we estimate noise given fixed experimental resources. We demonstrate the scalability and performance of our protocol through circuit-level numerical simulations of the entire noise-characterization procedure for the syndrome-extraction circuit of a distance-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mn>25</a:mn></a:math> surface code with over <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><d:mn>1000</d:mn></d:math> qubits. Our results indicate that detailed noise-characterization methods are scalable to near-term quantum devices.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Characterizing the performance of noisy quantum circuits is central to the production of prototype quantum computers and can enable improved quantum error correction that exploits noise biases identified in a quantum device. We develop a scalable noise-characterization protocol suited to characterizing the syndrome-extraction circuits of quantum error-correcting codes, a key component of fault-tolerant architectures. Our protocol builds upon averaged circuit eigenvalue sampling (ACES), a framework for noise-characterization experiments that simultaneously estimates the Pauli-error probabilities of all gates in a Clifford circuit and captures averaged spatial correlations between gates implemented simultaneously in the layers of the circuit. By rigorously analyzing the performance of noise-characterization experiments in the ACES framework, we derive a figure of merit for their expected performance, allowing us to optimize their experimental design and improve the precision to which we estimate noise given fixed experimental resources. We demonstrate the scalability and performance of our protocol through circuit-level numerical simulations of the entire noise-characterization procedure for the syndrome-extraction circuit of a distance-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mn>25</a:mn></a:math> surface code with over <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><d:mn>1000</d:mn></d:math> qubits. Our results indicate that detailed noise-characterization methods are scalable to near-term quantum devices.</jats:p>
E. N. Ivanov
Microwave Armstrong Amplitude Modulator Journal Article
In: IEEE Microw. Wireless Tech. Lett., vol. 35, no. 2, pp. 229–232, 2025, ISSN: 2771-9588.
@article{Ivanov2025,
title = {Microwave Armstrong Amplitude Modulator},
author = {E. N. Ivanov},
doi = {10.1109/lmwt.2024.3513315},
issn = {2771-9588},
year = {2025},
date = {2025-02-00},
urldate = {2025-02-00},
journal = {IEEE Microw. Wireless Tech. Lett.},
volume = {35},
number = {2},
pages = {229--232},
publisher = {Institute of Electrical and Electronics Engineers (IEEE)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A. Hahn; P. Hartung; D. Burgarth; P. Facchi; K. Yuasa
Lower bounds for the Trotter error Journal Article
In: Phys. Rev. A, vol. 111, no. 2, 2025, ISSN: 2469-9934.
@article{Hahn2025,
title = {Lower bounds for the Trotter error},
author = {A. Hahn and P. Hartung and D. Burgarth and P. Facchi and K. Yuasa},
doi = {10.1103/physreva.111.022417},
issn = {2469-9934},
year = {2025},
date = {2025-02-00},
urldate = {2025-02-00},
journal = {Phys. Rev. A},
volume = {111},
number = {2},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A. Hahn; K. Yuasa; D. Burgarth
Bath dynamical decoupling with a quantum channel Journal Article
In: J. Phys. A: Math. Theor., vol. 58, no. 4, 2025, ISSN: 1751-8121.
Abstract | Links | BibTeX | Tags:
@article{Hahn2025b,
title = {Bath dynamical decoupling with a quantum channel},
author = {A. Hahn and K. Yuasa and D. Burgarth},
doi = {10.1088/1751-8121/ada219},
issn = {1751-8121},
year = {2025},
date = {2025-01-27},
urldate = {2025-01-27},
journal = {J. Phys. A: Math. Theor.},
volume = {58},
number = {4},
publisher = {IOP Publishing},
abstract = {<jats:title>Abstract</jats:title>
<jats:p>Bang–bang dynamical decoupling protects an open quantum system from decoherence due to its interaction with the surrounding bath/environment. In its standard form, this is achieved by strongly kicking the system with cycles of unitary operations, which average out the interaction Hamiltonian. In this paper, we generalize the notion of dynamical decoupling to repeated kicks with a quantum channel, which is applied to the bath. We derive necessary and sufficient conditions on the employed quantum channel and find that bath dynamical decoupling works if and only if the kick is ergodic. Furthermore, we study in which circumstances completely positive trace-preserving (CPTP) kicks on a mono-partite quantum system induce quantum Zeno dynamics with its Hamiltonian cancelled out. This does not require the ergodicity of the kicks, and the absence of decoherence-free subsystems is both necessary and sufficient. While the standard unitary dynamical decoupling is essentially the same as the quantum Zeno dynamics, our investigation implies that this is no longer true in the case of CPTP kicks. To derive our results, we prove some spectral properties of ergodic quantum channels, that might be of independent interest. Our approach establishes an enhanced and unified mathematical understanding of several recent experimental demonstrations and might form the basis of new dynamical decoupling schemes that harness environmental noise degrees of freedom.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title>
<jats:p>Bang–bang dynamical decoupling protects an open quantum system from decoherence due to its interaction with the surrounding bath/environment. In its standard form, this is achieved by strongly kicking the system with cycles of unitary operations, which average out the interaction Hamiltonian. In this paper, we generalize the notion of dynamical decoupling to repeated kicks with a quantum channel, which is applied to the bath. We derive necessary and sufficient conditions on the employed quantum channel and find that bath dynamical decoupling works if and only if the kick is ergodic. Furthermore, we study in which circumstances completely positive trace-preserving (CPTP) kicks on a mono-partite quantum system induce quantum Zeno dynamics with its Hamiltonian cancelled out. This does not require the ergodicity of the kicks, and the absence of decoherence-free subsystems is both necessary and sufficient. While the standard unitary dynamical decoupling is essentially the same as the quantum Zeno dynamics, our investigation implies that this is no longer true in the case of CPTP kicks. To derive our results, we prove some spectral properties of ergodic quantum channels, that might be of independent interest. Our approach establishes an enhanced and unified mathematical understanding of several recent experimental demonstrations and might form the basis of new dynamical decoupling schemes that harness environmental noise degrees of freedom.</jats:p>
<jats:p>Bang–bang dynamical decoupling protects an open quantum system from decoherence due to its interaction with the surrounding bath/environment. In its standard form, this is achieved by strongly kicking the system with cycles of unitary operations, which average out the interaction Hamiltonian. In this paper, we generalize the notion of dynamical decoupling to repeated kicks with a quantum channel, which is applied to the bath. We derive necessary and sufficient conditions on the employed quantum channel and find that bath dynamical decoupling works if and only if the kick is ergodic. Furthermore, we study in which circumstances completely positive trace-preserving (CPTP) kicks on a mono-partite quantum system induce quantum Zeno dynamics with its Hamiltonian cancelled out. This does not require the ergodicity of the kicks, and the absence of decoherence-free subsystems is both necessary and sufficient. While the standard unitary dynamical decoupling is essentially the same as the quantum Zeno dynamics, our investigation implies that this is no longer true in the case of CPTP kicks. To derive our results, we prove some spectral properties of ergodic quantum channels, that might be of independent interest. Our approach establishes an enhanced and unified mathematical understanding of several recent experimental demonstrations and might form the basis of new dynamical decoupling schemes that harness environmental noise degrees of freedom.</jats:p>
S.-H. Lee; A. Li; S. D. Bartlett
Color code decoder with improved scaling for correcting circuit-level noise Journal Article
In: Quantum, vol. 9, 2025, ISSN: 2521-327X.
Abstract | Links | BibTeX | Tags:
@article{Lee2025,
title = {Color code decoder with improved scaling for correcting circuit-level noise},
author = {S.-H. Lee and A. Li and S. D. Bartlett},
doi = {10.22331/q-2025-01-27-1609},
issn = {2521-327X},
year = {2025},
date = {2025-01-27},
urldate = {2025-01-27},
journal = {Quantum},
volume = {9},
publisher = {Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften},
abstract = {<jats:p>Two-dimensional color codes are a promising candidate for fault-tolerant quantum computing, as they have high encoding rates, transversal implementation of logical Clifford gates, and resource-efficient magic state preparation schemes. However, decoding color codes presents a significant challenge due to their structure, where elementary errors violate three checks instead of just two (a key feature in surface code decoding), and the complexity of extracting syndrome is greater. We introduce an efficient color-code decoder that tackles these issues by combining two matching decoders for each color, generalized to handle circuit-level noise by employing detector error models. We provide comprehensive analyses of the decoder, covering its threshold and sub-threshold scaling both for bit-flip noise with ideal measurements and for circuit-level noise. Our simulations reveal that this decoding strategy nearly reaches the best possible scaling of logical failure (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>p</mml:mi><mml:mrow class="MJX-TeXAtom-ORD"><mml:mi mathvariant="normal">f</mml:mi><mml:mi mathvariant="normal">a</mml:mi><mml:mi mathvariant="normal">i</mml:mi><mml:mi mathvariant="normal">l</mml:mi></mml:mrow></mml:msub><mml:mo>∼</mml:mo><mml:msup><mml:mi>p</mml:mi><mml:mrow class="MJX-TeXAtom-ORD"><mml:mi>d</mml:mi><mml:mrow class="MJX-TeXAtom-ORD"><mml:mo>/</mml:mo></mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:math>) for both noise models, where <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>p</mml:mi></mml:math> is the noise strength, in the regime of interest for fault-tolerant quantum computing. While its noise thresholds are comparable with other matching-based decoders for color codes (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>8.2</mml:mn><mml:mi mathvariant="normal">%</mml:mi></mml:math> for bit-flip noise and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>0.46</mml:mn><mml:mi mathvariant="normal">%</mml:mi></mml:math> for circuit-level noise), the scaling of logical failure rates below threshold significantly outperforms the best matching-based decoders.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Two-dimensional color codes are a promising candidate for fault-tolerant quantum computing, as they have high encoding rates, transversal implementation of logical Clifford gates, and resource-efficient magic state preparation schemes. However, decoding color codes presents a significant challenge due to their structure, where elementary errors violate three checks instead of just two (a key feature in surface code decoding), and the complexity of extracting syndrome is greater. We introduce an efficient color-code decoder that tackles these issues by combining two matching decoders for each color, generalized to handle circuit-level noise by employing detector error models. We provide comprehensive analyses of the decoder, covering its threshold and sub-threshold scaling both for bit-flip noise with ideal measurements and for circuit-level noise. Our simulations reveal that this decoding strategy nearly reaches the best possible scaling of logical failure (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>p</mml:mi><mml:mrow class="MJX-TeXAtom-ORD"><mml:mi mathvariant="normal">f</mml:mi><mml:mi mathvariant="normal">a</mml:mi><mml:mi mathvariant="normal">i</mml:mi><mml:mi mathvariant="normal">l</mml:mi></mml:mrow></mml:msub><mml:mo>∼</mml:mo><mml:msup><mml:mi>p</mml:mi><mml:mrow class="MJX-TeXAtom-ORD"><mml:mi>d</mml:mi><mml:mrow class="MJX-TeXAtom-ORD"><mml:mo>/</mml:mo></mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:math>) for both noise models, where <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>p</mml:mi></mml:math> is the noise strength, in the regime of interest for fault-tolerant quantum computing. While its noise thresholds are comparable with other matching-based decoders for color codes (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>8.2</mml:mn><mml:mi mathvariant="normal">%</mml:mi></mml:math> for bit-flip noise and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>0.46</mml:mn><mml:mi mathvariant="normal">%</mml:mi></mml:math> for circuit-level noise), the scaling of logical failure rates below threshold significantly outperforms the best matching-based decoders.</jats:p>
N. Baspin; V. Guruswami; A. Krishna; R. Li
Improved rate-distance trade-offs for quantum codes with restricted connectivity Journal Article
In: Quantum Sci. Technol., vol. 10, no. 1, 2025, ISSN: 2058-9565.
Abstract | Links | BibTeX | Tags:
@article{Baspin2024,
title = {Improved rate-distance trade-offs for quantum codes with restricted connectivity},
author = {N. Baspin and V. Guruswami and A. Krishna and R. Li},
doi = {10.1088/2058-9565/ad8370},
issn = {2058-9565},
year = {2025},
date = {2025-01-01},
urldate = {2025-01-01},
journal = {Quantum Sci. Technol.},
volume = {10},
number = {1},
publisher = {IOP Publishing},
abstract = {<jats:title>Abstract</jats:title>
<jats:p>For quantum error-correcting codes to be realizable, it is important that the qubits subject to the code constraints exhibit some form of limited connectivity. The works of Bravyi and Terhal (2009 <jats:italic>New J. Phys.</jats:italic>
<jats:bold>11</jats:bold> 043029) (BT) and Bravyi <jats:italic>et al</jats:italic> (2010 <jats:italic>Phys. Rev. Lett.</jats:italic>
<jats:bold>104</jats:bold> 050503) (BPT) established that geometric locality constrains code properties—for instance <jats:inline-formula>
<jats:tex-math/>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mo stretchy="false">[</mml:mo>
<mml:mstyle scriptlevel="0"/>
<mml:mo stretchy="false">[</mml:mo>
<mml:mi>n</mml:mi>
<mml:mo>,</mml:mo>
<mml:mi>k</mml:mi>
<mml:mo>,</mml:mo>
<mml:mi>d</mml:mi>
<mml:mo stretchy="false">]</mml:mo>
<mml:mstyle scriptlevel="0"/>
<mml:mo stretchy="false">]</mml:mo>
</mml:mrow>
</mml:math>
</jats:inline-formula> quantum codes defined by local checks on the <jats:italic>D</jats:italic>-dimensional lattice must obey <jats:inline-formula>
<jats:tex-math/>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mi>k</mml:mi>
<mml:msup>
<mml:mi>d</mml:mi>
<mml:mrow>
<mml:mn>2</mml:mn>
<mml:mrow>
<mml:mo>/</mml:mo>
</mml:mrow>
<mml:mo stretchy="false">(</mml:mo>
<mml:mi>D</mml:mi>
<mml:mo>−</mml:mo>
<mml:mn>1</mml:mn>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
</mml:msup>
<mml:mtext>⩽</mml:mtext>
<mml:mi>O</mml:mi>
<mml:mo stretchy="false">(</mml:mo>
<mml:mi>n</mml:mi>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
</mml:math>
</jats:inline-formula>. Baspin and Krishna (2022 <jats:italic>Quantum</jats:italic>
<jats:bold>6</jats:bold> 711) studied the more general question of how the connectivity graph associated with a quantum code constrains the code parameters. These trade-offs apply to a richer class of codes compared to the BPT and BT bounds, which only capture geometrically-local codes. We extend and improve this work, establishing a tighter dimension-distance trade-off as a function of the size of separators in the connectivity graph. We also obtain a distance bound that covers all stabilizer codes with a particular separation profile, rather than only LDPC codes.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title>
<jats:p>For quantum error-correcting codes to be realizable, it is important that the qubits subject to the code constraints exhibit some form of limited connectivity. The works of Bravyi and Terhal (2009 <jats:italic>New J. Phys.</jats:italic>
<jats:bold>11</jats:bold> 043029) (BT) and Bravyi <jats:italic>et al</jats:italic> (2010 <jats:italic>Phys. Rev. Lett.</jats:italic>
<jats:bold>104</jats:bold> 050503) (BPT) established that geometric locality constrains code properties—for instance <jats:inline-formula>
<jats:tex-math/>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mo stretchy="false">[</mml:mo>
<mml:mstyle scriptlevel="0"/>
<mml:mo stretchy="false">[</mml:mo>
<mml:mi>n</mml:mi>
<mml:mo>,</mml:mo>
<mml:mi>k</mml:mi>
<mml:mo>,</mml:mo>
<mml:mi>d</mml:mi>
<mml:mo stretchy="false">]</mml:mo>
<mml:mstyle scriptlevel="0"/>
<mml:mo stretchy="false">]</mml:mo>
</mml:mrow>
</mml:math>
</jats:inline-formula> quantum codes defined by local checks on the <jats:italic>D</jats:italic>-dimensional lattice must obey <jats:inline-formula>
<jats:tex-math/>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mi>k</mml:mi>
<mml:msup>
<mml:mi>d</mml:mi>
<mml:mrow>
<mml:mn>2</mml:mn>
<mml:mrow>
<mml:mo>/</mml:mo>
</mml:mrow>
<mml:mo stretchy="false">(</mml:mo>
<mml:mi>D</mml:mi>
<mml:mo>−</mml:mo>
<mml:mn>1</mml:mn>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
</mml:msup>
<mml:mtext>⩽</mml:mtext>
<mml:mi>O</mml:mi>
<mml:mo stretchy="false">(</mml:mo>
<mml:mi>n</mml:mi>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
</mml:math>
</jats:inline-formula>. Baspin and Krishna (2022 <jats:italic>Quantum</jats:italic>
<jats:bold>6</jats:bold> 711) studied the more general question of how the connectivity graph associated with a quantum code constrains the code parameters. These trade-offs apply to a richer class of codes compared to the BPT and BT bounds, which only capture geometrically-local codes. We extend and improve this work, establishing a tighter dimension-distance trade-off as a function of the size of separators in the connectivity graph. We also obtain a distance bound that covers all stabilizer codes with a particular separation profile, rather than only LDPC codes.</jats:p>
<jats:p>For quantum error-correcting codes to be realizable, it is important that the qubits subject to the code constraints exhibit some form of limited connectivity. The works of Bravyi and Terhal (2009 <jats:italic>New J. Phys.</jats:italic>
<jats:bold>11</jats:bold> 043029) (BT) and Bravyi <jats:italic>et al</jats:italic> (2010 <jats:italic>Phys. Rev. Lett.</jats:italic>
<jats:bold>104</jats:bold> 050503) (BPT) established that geometric locality constrains code properties—for instance <jats:inline-formula>
<jats:tex-math/>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mo stretchy="false">[</mml:mo>
<mml:mstyle scriptlevel="0"/>
<mml:mo stretchy="false">[</mml:mo>
<mml:mi>n</mml:mi>
<mml:mo>,</mml:mo>
<mml:mi>k</mml:mi>
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<mml:mi>d</mml:mi>
<mml:mo stretchy="false">]</mml:mo>
<mml:mstyle scriptlevel="0"/>
<mml:mo stretchy="false">]</mml:mo>
</mml:mrow>
</mml:math>
</jats:inline-formula> quantum codes defined by local checks on the <jats:italic>D</jats:italic>-dimensional lattice must obey <jats:inline-formula>
<jats:tex-math/>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mi>k</mml:mi>
<mml:msup>
<mml:mi>d</mml:mi>
<mml:mrow>
<mml:mn>2</mml:mn>
<mml:mrow>
<mml:mo>/</mml:mo>
</mml:mrow>
<mml:mo stretchy="false">(</mml:mo>
<mml:mi>D</mml:mi>
<mml:mo>−</mml:mo>
<mml:mn>1</mml:mn>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
</mml:msup>
<mml:mtext>⩽</mml:mtext>
<mml:mi>O</mml:mi>
<mml:mo stretchy="false">(</mml:mo>
<mml:mi>n</mml:mi>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
</mml:math>
</jats:inline-formula>. Baspin and Krishna (2022 <jats:italic>Quantum</jats:italic>
<jats:bold>6</jats:bold> 711) studied the more general question of how the connectivity graph associated with a quantum code constrains the code parameters. These trade-offs apply to a richer class of codes compared to the BPT and BT bounds, which only capture geometrically-local codes. We extend and improve this work, establishing a tighter dimension-distance trade-off as a function of the size of separators in the connectivity graph. We also obtain a distance bound that covers all stabilizer codes with a particular separation profile, rather than only LDPC codes.</jats:p>