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
L. A. Williamson; F. Cerisola; J. Anders; M. J. Davis
Extracting work from coherence in a two-mode Bose–Einstein condensate Journal Article
In: Quantum Sci. Technol., vol. 10, no. 1, 2025, ISSN: 2058-9565.
Abstract | Links | BibTeX | Tags:
@article{Williamson2024,
title = {Extracting work from coherence in a two-mode Bose–Einstein condensate},
author = {L. A. Williamson and F. Cerisola and J. Anders and M. J. Davis},
doi = {10.1088/2058-9565/ad8fc9},
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>We show how work can be extracted from number-state coherence in a two-mode Bose–Einstein condensate. With careful tuning of parameters, a sequence of thermodynamically reversible steps transforms a Glauber coherent state into a thermal state with the same energy probability distribution. The work extracted during this process arises entirely from the removal of quantum coherence. More generally, we characterise quantum (from coherence) and classical (remaining) contributions to work output, and find that in this system the quantum contribution can be dominant over a broad range of parameters. The proportion of quantum work output can be further enhanced by squeezing the initial state. Due to the many-body nature of the system, the work from coherence can equivalently be understood as work from entanglement.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title>
<jats:p>We show how work can be extracted from number-state coherence in a two-mode Bose–Einstein condensate. With careful tuning of parameters, a sequence of thermodynamically reversible steps transforms a Glauber coherent state into a thermal state with the same energy probability distribution. The work extracted during this process arises entirely from the removal of quantum coherence. More generally, we characterise quantum (from coherence) and classical (remaining) contributions to work output, and find that in this system the quantum contribution can be dominant over a broad range of parameters. The proportion of quantum work output can be further enhanced by squeezing the initial state. Due to the many-body nature of the system, the work from coherence can equivalently be understood as work from entanglement.</jats:p>
<jats:p>We show how work can be extracted from number-state coherence in a two-mode Bose–Einstein condensate. With careful tuning of parameters, a sequence of thermodynamically reversible steps transforms a Glauber coherent state into a thermal state with the same energy probability distribution. The work extracted during this process arises entirely from the removal of quantum coherence. More generally, we characterise quantum (from coherence) and classical (remaining) contributions to work output, and find that in this system the quantum contribution can be dominant over a broad range of parameters. The proportion of quantum work output can be further enhanced by squeezing the initial state. Due to the many-body nature of the system, the work from coherence can equivalently be understood as work from entanglement.</jats:p>
Y-J. Tan; W-S. Huang; P-P. Wang; Z-Q. Wu; J-M. L. Floch; H-Z. Wu; J. Liu; C-G. Shao; Z-B. Zhou
Time-delay interferometry combinations to suppress two of six test-mass disturbances in space-borne gravitational wave detectors Journal Article
In: Phys. Rev. D, vol. 111, no. 2, 2025, ISSN: 2470-0029.
@article{Tan2025,
title = {Time-delay interferometry combinations to suppress two of six test-mass disturbances in space-borne gravitational wave detectors},
author = {Y-J. Tan and W-S. Huang and P-P. Wang and Z-Q. Wu and J-M. L. Floch and H-Z. Wu and J. Liu and C-G. Shao and Z-B. Zhou},
doi = {10.1103/physrevd.111.024011},
issn = {2470-0029},
year = {2025},
date = {2025-01-00},
urldate = {2025-01-00},
journal = {Phys. Rev. D},
volume = {111},
number = {2},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
F. Wang; M. Ren; W. Sun; M. Guo; M. J. Sellars; R. L. Ahlefeldt; J. G. Bartholomew; J. Yao; S. Liu; M. Zhong
Nuclear Spins in a Solid Exceeding 10-Hour Coherence Times for Ultra-Long-Term Quantum Storage Journal Article
In: PRX Quantum, vol. 6, no. 1, 2025, ISSN: 2691-3399.
Abstract | Links | BibTeX | Tags:
@article{Wang2025,
title = {Nuclear Spins in a Solid Exceeding 10-Hour Coherence Times for Ultra-Long-Term Quantum Storage},
author = {F. Wang and M. Ren and W. Sun and M. Guo and M. J. Sellars and R. L. Ahlefeldt and J. G. Bartholomew and J. Yao and S. Liu and M. Zhong},
doi = {10.1103/prxquantum.6.010302},
issn = {2691-3399},
year = {2025},
date = {2025-01-00},
urldate = {2025-01-00},
journal = {PRX Quantum},
volume = {6},
number = {1},
publisher = {American Physical Society (APS)},
abstract = {<jats:p>Long-term quantum storage for quantum communication applications will require optically accessible states with coherence times exceeding the desired storage time. Ground-state hyperfine levels in <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mi>Eu</a:mi></a:math><d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><d:msup><d:mi/><d:mrow><d:mn>3</d:mn><d:mo>+</d:mo></d:mrow></d:msup></d:math>:<g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><g:mrow><g:mrow><g:mi mathvariant="normal">Y</g:mi></g:mrow></g:mrow></g:math><k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><k:msub><k:mi/><k:mn>2</k:mn></k:msub></k:math><n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><n:mrow><n:mi>Si</n:mi><n:mi mathvariant="normal">O</n:mi></n:mrow></n:math><r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><r:msub><r:mi/><r:mn>5</r:mn></r:msub></r:math> have previously shown coherence times as long as 6 h at 1.4 K when operated at a zero-first-order-Zeeman (ZEFOZ) point. Here, we have characterized the limiting decoherence mechanisms acting in this regime, which shows that the coherence time is limited by the presence of spin impurities. This dephasing effect has been suppressed by cooling the sample to 125 mK, resulting in an extension in the coherence time to over 13 h. In the absence of these impurities, the dominant source of dephasing is the field inhomogeneity of the ZEFOZ point arising from the spin inhomogeneous broadening. We have shown that coherence times over 18 h can be achieved by operating using a spectrally narrow subensemble selected from within the inhomogeneous line. The observed coherence time is longer than that of any other system suitable for an optical quantum memory. Furthermore, at a much higher temperature of 6 K, we have realized a 6-h coherence time, which has been obtainable using single-stage cryocoolers. These results imply advanced engineering feasibility in designing and operating future quantum information-storage devices for a wide range of applications, including in satellites.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Long-term quantum storage for quantum communication applications will require optically accessible states with coherence times exceeding the desired storage time. Ground-state hyperfine levels in <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mi>Eu</a:mi></a:math><d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><d:msup><d:mi/><d:mrow><d:mn>3</d:mn><d:mo>+</d:mo></d:mrow></d:msup></d:math>:<g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><g:mrow><g:mrow><g:mi mathvariant="normal">Y</g:mi></g:mrow></g:mrow></g:math><k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><k:msub><k:mi/><k:mn>2</k:mn></k:msub></k:math><n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><n:mrow><n:mi>Si</n:mi><n:mi mathvariant="normal">O</n:mi></n:mrow></n:math><r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><r:msub><r:mi/><r:mn>5</r:mn></r:msub></r:math> have previously shown coherence times as long as 6 h at 1.4 K when operated at a zero-first-order-Zeeman (ZEFOZ) point. Here, we have characterized the limiting decoherence mechanisms acting in this regime, which shows that the coherence time is limited by the presence of spin impurities. This dephasing effect has been suppressed by cooling the sample to 125 mK, resulting in an extension in the coherence time to over 13 h. In the absence of these impurities, the dominant source of dephasing is the field inhomogeneity of the ZEFOZ point arising from the spin inhomogeneous broadening. We have shown that coherence times over 18 h can be achieved by operating using a spectrally narrow subensemble selected from within the inhomogeneous line. The observed coherence time is longer than that of any other system suitable for an optical quantum memory. Furthermore, at a much higher temperature of 6 K, we have realized a 6-h coherence time, which has been obtainable using single-stage cryocoolers. These results imply advanced engineering feasibility in designing and operating future quantum information-storage devices for a wide range of applications, including in satellites.</jats:p>
L. A. Williamson
Modified Jarzynski equality in a microcanonical ensemble Journal Article
In: Phys. Rev. E, vol. 111, no. 1, 2025, ISSN: 2470-0053.
@article{Williamson2025,
title = {Modified Jarzynski equality in a microcanonical ensemble},
author = {L. A. Williamson},
doi = {10.1103/physreve.111.l012102},
issn = {2470-0053},
year = {2025},
date = {2025-01-00},
journal = {Phys. Rev. E},
volume = {111},
number = {1},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
O. Raii; A. Dey; F. Mintert; D. Burgarth
Creation and manipulation of surface code defects with quantum optimal control Journal Article
In: Phys. Rev. A, vol. 111, no. 1, 2025, ISSN: 2469-9934.
@article{Raii2025,
title = {Creation and manipulation of surface code defects with quantum optimal control},
author = {O. Raii and A. Dey and F. Mintert and D. Burgarth},
doi = {10.1103/physreva.111.012423},
issn = {2469-9934},
year = {2025},
date = {2025-01-00},
urldate = {2025-01-00},
journal = {Phys. Rev. A},
volume = {111},
number = {1},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
E. Wagner; F. Dell’Anna; R. Nigmatullin; G. K. Brennen
Density Classification with Non-Unitary Quantum Cellular Automata Journal Article
In: Entropy, vol. 27, no. 1, 2025, ISSN: 1099-4300.
Abstract | Links | BibTeX | Tags:
@article{Wagner2024,
title = {Density Classification with Non-Unitary Quantum Cellular Automata},
author = {E. Wagner and F. Dell’Anna and R. Nigmatullin and G. K. Brennen},
doi = {10.3390/e27010026},
issn = {1099-4300},
year = {2025},
date = {2025-01-00},
urldate = {2025-01-00},
journal = {Entropy},
volume = {27},
number = {1},
publisher = {MDPI AG},
abstract = {<jats:p>The density classification (DC) task, a computation which maps global density information to local density, is studied using one-dimensional non-unitary quantum cellular automata (QCAs). Two approaches are considered: one that preserves the number density and one that performs majority voting. For number-preserving DC, two QCAs are introduced that reach the fixed-point solution in a time scaling quadratically with the system size. One of the QCAs is based on a known classical probabilistic cellular automaton which has been studied in the context of DC. The second is a new quantum model that is designed to demonstrate additional quantum features and is restricted to only two-body interactions. Both can be generated by continuous-time Lindblad dynamics. A third QCA is a hybrid rule defined by both discrete-time and continuous-time three-body interactions that is shown to solve the majority voting problem within a time that scales linearly with the system size.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>The density classification (DC) task, a computation which maps global density information to local density, is studied using one-dimensional non-unitary quantum cellular automata (QCAs). Two approaches are considered: one that preserves the number density and one that performs majority voting. For number-preserving DC, two QCAs are introduced that reach the fixed-point solution in a time scaling quadratically with the system size. One of the QCAs is based on a known classical probabilistic cellular automaton which has been studied in the context of DC. The second is a new quantum model that is designed to demonstrate additional quantum features and is restricted to only two-body interactions. Both can be generated by continuous-time Lindblad dynamics. A third QCA is a hybrid rule defined by both discrete-time and continuous-time three-body interactions that is shown to solve the majority voting problem within a time that scales linearly with the system size.</jats:p>
L. R. McQueen; N. Bawden; B. J. Carey; I. Marinkovi; W. P. Bowen; G. I. Harris
Fibre-coupled photonic crystal hydrophone Journal Article
In: Opt. Express, vol. 33, no. 12, 2025, ISSN: 1094-4087.
Abstract | Links | BibTeX | Tags:
@article{McQueen2025,
title = {Fibre-coupled photonic crystal hydrophone},
author = {L. R. McQueen and N. Bawden and B. J. Carey and I. Marinkovi and W. P. Bowen and G. I. Harris},
doi = {10.1364/oe.557657},
issn = {1094-4087},
year = {2025},
date = {2025-00-00},
urldate = {2025-00-00},
journal = {Opt. Express},
volume = {33},
number = {12},
publisher = {Optica Publishing Group},
abstract = {<jats:p>Many applications, including industrial processes, sonar, and navigation, rely on the detection of acoustic waves. Photonic hydrophones demonstrate comparable sensitivity to piezoelectric-based hydrophones but with significantly reduced size, weight, and power requirements. In this paper, we demonstrate a micron-sized free-standing silicon photonic hydrophone. We demonstrate sensitivity on the order of ?mPa/Hz from 10-200 kHz, with a minimum detectable pressure of 145 Pa/Hz at 22 kHz. We also deployed our hydrophone in a wave flume to evaluate its suitability for underwater measurement and communication. Our hydrophone matches the sensitivity of commercial hydrophones but is many orders of magnitude smaller in volume, which could enable high spatial resolution imaging of micron-sized acoustic features (<jats:italic toggle="yes">i.e.</jats:italic>, living cell vibrations). Our hydrophone could also be used in underwater communication and imaging applications.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Many applications, including industrial processes, sonar, and navigation, rely on the detection of acoustic waves. Photonic hydrophones demonstrate comparable sensitivity to piezoelectric-based hydrophones but with significantly reduced size, weight, and power requirements. In this paper, we demonstrate a micron-sized free-standing silicon photonic hydrophone. We demonstrate sensitivity on the order of ?mPa/Hz from 10-200 kHz, with a minimum detectable pressure of 145 Pa/Hz at 22 kHz. We also deployed our hydrophone in a wave flume to evaluate its suitability for underwater measurement and communication. Our hydrophone matches the sensitivity of commercial hydrophones but is many orders of magnitude smaller in volume, which could enable high spatial resolution imaging of micron-sized acoustic features (<jats:italic toggle="yes">i.e.</jats:italic>, living cell vibrations). Our hydrophone could also be used in underwater communication and imaging applications.</jats:p>
S. R. Nair; F. A. Hahl; A. D. Greentree; J. Jeske; T. Volz
Diamond laser threshold magnetometer Book Chapter
In: Nanophotonics with Diamond and Silicon Carbide for Quantum Technologies, pp. 219–228, Elsevier, 2025, ISBN: 9780443137174.
@inbook{RamanNair2025,
title = {Diamond laser threshold magnetometer},
author = {S. R. Nair and F. A. Hahl and A. D. Greentree and J. Jeske and T. Volz},
doi = {10.1016/b978-0-443-13717-4.00012-8},
isbn = {9780443137174},
year = {2025},
date = {2025-00-00},
urldate = {2025-00-00},
booktitle = {Nanophotonics with Diamond and Silicon Carbide for Quantum Technologies},
pages = {219--228},
publisher = {Elsevier},
keywords = {},
pubstate = {published},
tppubtype = {inbook}
}
J. A. Rowland; C. Perrella; R. F. Offer; A. N. Luiten; B. M. Sparkes; T. J. Weinhold
Characterization of near-infrared to telecom frequency conversion in a rubidium-filled hollow-core photonic-crystal fiber Journal Article
In: Opt. Express, vol. 33, no. 8, 2025, ISSN: 1094-4087.
Abstract | Links | BibTeX | Tags:
@article{Rowland2025,
title = {Characterization of near-infrared to telecom frequency conversion in a rubidium-filled hollow-core photonic-crystal fiber},
author = {J. A. Rowland and C. Perrella and R. F. Offer and A. N. Luiten and B. M. Sparkes and T. J. Weinhold},
doi = {10.1364/oe.549459},
issn = {1094-4087},
year = {2025},
date = {2025-00-00},
urldate = {2025-00-00},
journal = {Opt. Express},
volume = {33},
number = {8},
publisher = {Optica Publishing Group},
abstract = {<jats:p>We experimentally investigate near-infrared to telecommunications frequency conversion via a diamond four-wave mixing scheme in rubidium vapor contained within a hollow-core photonic-crystal fiber. The strong light-atom interaction in the fiber results in lower pump power requirements and higher conversion efficiency than can be achieved under equivalent conditions in a rubidium vapor cell. We also observe non-intuitive pump and signal frequency dependence of the four-wave mixing efficiency in the fiber due to the large nonlinearities present in the system. These results indicate the potential for hollow-core fibers to provide a scalable solution for quantum information network infrastructure, with additional modelling required for a full understanding of the extreme atom-light interaction effects present.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>We experimentally investigate near-infrared to telecommunications frequency conversion via a diamond four-wave mixing scheme in rubidium vapor contained within a hollow-core photonic-crystal fiber. The strong light-atom interaction in the fiber results in lower pump power requirements and higher conversion efficiency than can be achieved under equivalent conditions in a rubidium vapor cell. We also observe non-intuitive pump and signal frequency dependence of the four-wave mixing efficiency in the fiber due to the large nonlinearities present in the system. These results indicate the potential for hollow-core fibers to provide a scalable solution for quantum information network infrastructure, with additional modelling required for a full understanding of the extreme atom-light interaction effects present.</jats:p>
P-S. Hsin; D. Stephen; A. Dua; D. J. Williamson
Subsystem symmetry fractionalization and foliated field theory Journal Article
In: SciPost Phys., vol. 18, no. 5, 2025, ISSN: 2542-4653.
Abstract | Links | BibTeX | Tags:
@article{Hsin2025,
title = {Subsystem symmetry fractionalization and foliated field theory},
author = {P-S. Hsin and D. Stephen and A. Dua and D. J. Williamson},
doi = {10.21468/scipostphys.18.5.147},
issn = {2542-4653},
year = {2025},
date = {2025-00-00},
urldate = {2025-00-00},
journal = {SciPost Phys.},
volume = {18},
number = {5},
publisher = {Stichting SciPost},
abstract = {<jats:p>Topological quantum matter exhibits a range of exotic phenomena when enriched by subdimensional symmetries. This includes new features beyond those that appear in the conventional setting of global symmetry enrichment. A recently discovered example is a type of subsystem symmetry fractionalization that occurs through a different mechanism to global symmetry fractionalization. In this work we extend the study of subsystem symmetry fractionalization through new examples derived from the general principle of embedding subsystem symmetry into higher-form symmetry. This leads to new types of symmetry fractionalization that are described by foliation dependent higher-form symmetries. This leads to field theories and lattice models that support previously unseen anomalous subsystem symmetry fractionalization. Our work expands the range of exotic topological physics that is enabled by subsystem symmetry in field theory and on the lattice.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Topological quantum matter exhibits a range of exotic phenomena when enriched by subdimensional symmetries. This includes new features beyond those that appear in the conventional setting of global symmetry enrichment. A recently discovered example is a type of subsystem symmetry fractionalization that occurs through a different mechanism to global symmetry fractionalization. In this work we extend the study of subsystem symmetry fractionalization through new examples derived from the general principle of embedding subsystem symmetry into higher-form symmetry. This leads to new types of symmetry fractionalization that are described by foliation dependent higher-form symmetries. This leads to field theories and lattice models that support previously unseen anomalous subsystem symmetry fractionalization. Our work expands the range of exotic topological physics that is enabled by subsystem symmetry in field theory and on the lattice.</jats:p>
J. S. Wallis; D. R. Gozzard; A. Frost; J. J. Collier; N. Maron; B. P. Dix-Matthews
Spatial mode demultiplexing for super-resolved source parameter estimation Journal Article
In: Opt. Express, vol. 33, no. 16, 2025, ISSN: 1094-4087.
Abstract | Links | BibTeX | Tags:
@article{Wallis2025,
title = {Spatial mode demultiplexing for super-resolved source parameter estimation},
author = {J. S. Wallis and D. R. Gozzard and A. Frost and J. J. Collier and N. Maron and B. P. Dix-Matthews},
doi = {10.1364/oe.563503},
issn = {1094-4087},
year = {2025},
date = {2025-00-00},
urldate = {2025-00-00},
journal = {Opt. Express},
volume = {33},
number = {16},
publisher = {Optica Publishing Group},
abstract = {<jats:p>We present the use of a multi-planar light converter (MPLC) to perform spatial mode demultiplexing (SPADE) for optical source parameter estimation. This technique has been extended to use higher-order Hermite-Gaussian modes for the purposes of estimating the separation of a pair of incoherent sources, both above and below the diffraction limit. We resolve these sources at separations 90× lower than the diffraction limit. We also show our system is capable of simultaneous separation estimation and relative power estimation while maintaining super-resolving capabilities, with relative power differences as large as 20 dB by using the additional information gained by incorporation of the higher order modes. These results support the potential use of SPADE for astronomical imaging of binary systems.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>We present the use of a multi-planar light converter (MPLC) to perform spatial mode demultiplexing (SPADE) for optical source parameter estimation. This technique has been extended to use higher-order Hermite-Gaussian modes for the purposes of estimating the separation of a pair of incoherent sources, both above and below the diffraction limit. We resolve these sources at separations 90× lower than the diffraction limit. We also show our system is capable of simultaneous separation estimation and relative power estimation while maintaining super-resolving capabilities, with relative power differences as large as 20 dB by using the additional information gained by incorporation of the higher order modes. These results support the potential use of SPADE for astronomical imaging of binary systems.</jats:p>
M. L. Watson; A. B. Stilgoe; I. A. Favre-Bulle; H. Rubinsztein-Dunlop
Interrogating the ballistic regime in liquids with rotational optical tweezers Journal Article
In: Optica, vol. 12, no. 2, 2025, ISSN: 2334-2536.
Abstract | Links | BibTeX | Tags:
@article{Watson2025,
title = {Interrogating the ballistic regime in liquids with rotational optical tweezers},
author = {M. L. Watson and A. B. Stilgoe and I. A. Favre-Bulle and H. Rubinsztein-Dunlop},
doi = {10.1364/optica.549215},
issn = {2334-2536},
year = {2025},
date = {2025-00-00},
urldate = {2025-00-00},
journal = {Optica},
volume = {12},
number = {2},
publisher = {Optica Publishing Group},
abstract = {<jats:p>Accessing the ballistic regime of single particles in liquids remains an experimental challenge that shrouds our understanding of particle–liquid interactions on exceedingly short time scales. We demonstrate rotational ballistic measurements of microspheres in liquids by observing the thermalization of the angular velocity. This study uses sensitive high-bandwidth polarization measurements from light scattered by orientation-locked birefringent probes trapped with rotational optical tweezers. The particle–liquid interactions in the ballistic regime are decoupled from the optical potential allowing direct studies of single-particle rotational dynamics in a previously inaccessible parameter space. This enabled us to observe and validate rotational hydrodynamic effects and perform ultrafast calibration-free viscometry using less than 50 ms of data. This methodology establishes a unique tool for studying microscopic rotational dynamics and probing highly dynamic microenvironments, including systems out of equilibrium.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Accessing the ballistic regime of single particles in liquids remains an experimental challenge that shrouds our understanding of particle–liquid interactions on exceedingly short time scales. We demonstrate rotational ballistic measurements of microspheres in liquids by observing the thermalization of the angular velocity. This study uses sensitive high-bandwidth polarization measurements from light scattered by orientation-locked birefringent probes trapped with rotational optical tweezers. The particle–liquid interactions in the ballistic regime are decoupled from the optical potential allowing direct studies of single-particle rotational dynamics in a previously inaccessible parameter space. This enabled us to observe and validate rotational hydrodynamic effects and perform ultrafast calibration-free viscometry using less than 50 ms of data. This methodology establishes a unique tool for studying microscopic rotational dynamics and probing highly dynamic microenvironments, including systems out of equilibrium.</jats:p>
J. J. Collier; D. R. Gozzard; J. S. Wallis; S. M. P. McSorely
Feasibility of phase stabilization for satellite-mediated twin-field quantum key distribution Journal Article
In: Opt. Lett., vol. 50, no. 2, 2025, ISSN: 1539-4794.
Abstract | Links | BibTeX | Tags:
@article{Collier2025,
title = {Feasibility of phase stabilization for satellite-mediated twin-field quantum key distribution},
author = {J. J. Collier and D. R. Gozzard and J. S. Wallis and S. M. P. McSorely},
doi = {10.1364/ol.541228},
issn = {1539-4794},
year = {2025},
date = {2025-00-00},
urldate = {2025-00-00},
journal = {Opt. Lett.},
volume = {50},
number = {2},
publisher = {Optica Publishing Group},
abstract = {<jats:p>Quantum key distribution (QKD) is critical for future proofed secure communication. Satellites will be necessary to mediate QKD on a global scale. The limitations of the existing quantum memory and repeater technology mean that twin-field QKD (TF-QKD) provides the most feasible near-term solution to perform QKD with an untrusted satellite. However, the TF-QKD requires links between ground stations and satellites to be phase stable. We show that phase stabilization of the links to LEO and MEO satellites is feasible in spite of phase noise due to atmospheric turbulence, laser instability, and path length asymmetry while only incurring a quantum bit error rate (QBER) penalty of less than 1.5%. These results are also applicable to future untrusted satellite networks employing precisely synchronized quantum memories or quantum repeaters.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Quantum key distribution (QKD) is critical for future proofed secure communication. Satellites will be necessary to mediate QKD on a global scale. The limitations of the existing quantum memory and repeater technology mean that twin-field QKD (TF-QKD) provides the most feasible near-term solution to perform QKD with an untrusted satellite. However, the TF-QKD requires links between ground stations and satellites to be phase stable. We show that phase stabilization of the links to LEO and MEO satellites is feasible in spite of phase noise due to atmospheric turbulence, laser instability, and path length asymmetry while only incurring a quantum bit error rate (QBER) penalty of less than 1.5%. These results are also applicable to future untrusted satellite networks employing precisely synchronized quantum memories or quantum repeaters.</jats:p>
Z. L. Stevens-Hough; M. J. Davis; L. Williamson
Dynamics of polar-core spin vortices in inhomogeneous spin-1 Bose-Einstein condensates Journal Article
In: SciPost Phys., vol. 18, no. 4, 2025, ISSN: 2542-4653.
Abstract | Links | BibTeX | Tags:
@article{Stevens-Hough2025,
title = {Dynamics of polar-core spin vortices in inhomogeneous spin-1 Bose-Einstein condensates},
author = {Z. L. Stevens-Hough and M. J. Davis and L. Williamson},
doi = {10.21468/scipostphys.18.4.134},
issn = {2542-4653},
year = {2025},
date = {2025-00-00},
urldate = {2025-00-00},
journal = {SciPost Phys.},
volume = {18},
number = {4},
publisher = {Stichting SciPost},
abstract = {<jats:p>In the easy-plane phase, a ferromagnetic spin-1 Bose-Einstein condensate is magnetized in a plane transverse to the applied Zeeman field. This phase supports polar-core spin vortices (PCVs), which consist of phase windings of transverse magnetization. Here we show that spin-changing collisions cause a PCV to accelerate down density gradients in an inhomogeneous condensate. The dynamics is well-described by a simplified model adapted from scalar systems, which predicts the dependence of the dynamics on trap tightness and quadratic Zeeman energy. In a harmonic trap, a PCV accelerates radially to the condensate boundary, in stark contrast to the azimuthal motion of vortices in a scalar condensate. In a trap that has a local potential maximum at the centre, the PCV exhibits oscillations around the trap centre, which persist for a remarkably long time. The oscillations coincide with the emission and reabsorption of axial spin waves, which reflect off the condensate boundary.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>In the easy-plane phase, a ferromagnetic spin-1 Bose-Einstein condensate is magnetized in a plane transverse to the applied Zeeman field. This phase supports polar-core spin vortices (PCVs), which consist of phase windings of transverse magnetization. Here we show that spin-changing collisions cause a PCV to accelerate down density gradients in an inhomogeneous condensate. The dynamics is well-described by a simplified model adapted from scalar systems, which predicts the dependence of the dynamics on trap tightness and quadratic Zeeman energy. In a harmonic trap, a PCV accelerates radially to the condensate boundary, in stark contrast to the azimuthal motion of vortices in a scalar condensate. In a trap that has a local potential maximum at the centre, the PCV exhibits oscillations around the trap centre, which persist for a remarkably long time. The oscillations coincide with the emission and reabsorption of axial spin waves, which reflect off the condensate boundary.</jats:p>
2024
K. A. Burch; S. Finlay-Smits; T. M. Roberson
Responsible innovation is not comfortable: a call for grounded, embodied reflexivity when doing RI Journal Article
In: Journal of Responsible Innovation, vol. 11, no. 1, 2024, ISSN: 2329-9037.
@article{Burch2024,
title = {Responsible innovation is not comfortable: a call for grounded, embodied reflexivity when doing RI},
author = {K. A. Burch and S. Finlay-Smits and T. M. Roberson},
doi = {10.1080/23299460.2024.2427429},
issn = {2329-9037},
year = {2024},
date = {2024-12-31},
urldate = {2024-12-31},
journal = {Journal of Responsible Innovation},
volume = {11},
number = {1},
publisher = {Informa UK Limited},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
L. J. Henderson; R. Goel; S. Shrapnel
Quantum Kernel Machine Learning With Continuous Variables Journal Article
In: Quantum, vol. 8, 2024, ISSN: 2521-327X.
Abstract | Links | BibTeX | Tags:
@article{Henderson2024,
title = {Quantum Kernel Machine Learning With Continuous Variables},
author = {L. J. Henderson and R. Goel and S. Shrapnel},
doi = {10.22331/q-2024-12-17-1570},
issn = {2521-327X},
year = {2024},
date = {2024-12-17},
urldate = {2024-12-17},
journal = {Quantum},
volume = {8},
publisher = {Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften},
abstract = {<jats:p>The popular qubit framework has dominated recent work on quantum kernel machine learning, with results characterising expressivity, learnability and generalisation. As yet, there is no comparative framework to understand these concepts for continuous variable (CV) quantum computing platforms. In this paper we represent CV quantum kernels as closed form functions and use this representation to provide several important theoretical insights. We derive a general closed form solution for all CV quantum kernels and show every such kernel can be expressed as the product of a Gaussian and an algebraic function of the parameters of the feature map. Furthermore, in the multi-mode case, we present quantification of a quantum-classical separation for all quantum kernels via a hierarchical notion of the “stellar rank" of the quantum kernel feature map. We then prove kernels defined by feature maps of infinite stellar rank, such as GKP-state encodings, can be approximated arbitrarily well by kernels defined by feature maps of finite stellar rank. Finally, we simulate learning with a single-mode displaced Fock state encoding and show that (i) accuracy on our specific task (an annular data set) increases with stellar rank, (ii) for underfit models, accuracy can be improved by increasing a bandwidth hyperparameter, and (iii) for noisy data that is overfit, decreasing the bandwidth will improve generalisation but does so at the cost of effective stellar rank.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>The popular qubit framework has dominated recent work on quantum kernel machine learning, with results characterising expressivity, learnability and generalisation. As yet, there is no comparative framework to understand these concepts for continuous variable (CV) quantum computing platforms. In this paper we represent CV quantum kernels as closed form functions and use this representation to provide several important theoretical insights. We derive a general closed form solution for all CV quantum kernels and show every such kernel can be expressed as the product of a Gaussian and an algebraic function of the parameters of the feature map. Furthermore, in the multi-mode case, we present quantification of a quantum-classical separation for all quantum kernels via a hierarchical notion of the “stellar rank" of the quantum kernel feature map. We then prove kernels defined by feature maps of infinite stellar rank, such as GKP-state encodings, can be approximated arbitrarily well by kernels defined by feature maps of finite stellar rank. Finally, we simulate learning with a single-mode displaced Fock state encoding and show that (i) accuracy on our specific task (an annular data set) increases with stellar rank, (ii) for underfit models, accuracy can be improved by increasing a bandwidth hyperparameter, and (iii) for noisy data that is overfit, decreasing the bandwidth will improve generalisation but does so at the cost of effective stellar rank.</jats:p>
S. Jandura; V. Srivastava; L. Pecorari; G. K. Brennen; G. Pupillo
Nonlocal multiqubit quantum gates via a driven cavity Journal Article
In: Phys. Rev. A, vol. 110, no. 6, 2024, ISSN: 2469-9934.
@article{Jandura2024,
title = {Nonlocal multiqubit quantum gates via a driven cavity},
author = {S. Jandura and V. Srivastava and L. Pecorari and G. K. Brennen and G. Pupillo},
doi = {10.1103/physreva.110.062610},
issn = {2469-9934},
year = {2024},
date = {2024-12-00},
urldate = {2024-12-00},
journal = {Phys. Rev. A},
volume = {110},
number = {6},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
S. C. Smith; B. J. Brown; S. D. Bartlett
Mitigating errors in logical qubits Journal Article
In: Commun Phys, vol. 7, no. 1, 2024, ISSN: 2399-3650.
@article{Smith2024,
title = {Mitigating errors in logical qubits},
author = {S. C. Smith and B. J. Brown and S. D. Bartlett},
doi = {10.1038/s42005-024-01883-4},
issn = {2399-3650},
year = {2024},
date = {2024-12-00},
urldate = {2024-12-00},
journal = {Commun Phys},
volume = {7},
number = {1},
publisher = {Springer Science and Business Media LLC},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A. S. Paul; S. K. Rajendran; D. Ziemkiewicz; T. Volz; H. Ohadi
Local tuning of Rydberg exciton energies in nanofabricated Cu2O pillars Journal Article
In: Commun Mater, vol. 5, no. 1, 2024, ISSN: 2662-4443.
Abstract | Links | BibTeX | Tags:
@article{Paul2024,
title = {Local tuning of Rydberg exciton energies in nanofabricated Cu2O pillars},
author = {A. S. Paul and S. K. Rajendran and D. Ziemkiewicz and T. Volz and H. Ohadi},
doi = {10.1038/s43246-024-00481-9},
issn = {2662-4443},
year = {2024},
date = {2024-12-00},
urldate = {2024-12-00},
journal = {Commun Mater},
volume = {5},
number = {1},
publisher = {Springer Science and Business Media LLC},
abstract = {<jats:title>Abstract</jats:title>
<jats:p>Rydberg excitons in Cu<jats:sub>2</jats:sub>O feature giant optical nonlinearities. To exploit these nonlinearities for quantum applications, the confinement must match the Rydberg blockade size, which in Cu<jats:sub>2</jats:sub>O could be as large as a few microns. Here, in a top-down approach, we show how exciton confinement can be realised by focused-ion-beam etching of a polished bulk Cu<jats:sub>2</jats:sub>O crystal without noticeable degradation of the excitonic properties. The etching of the crystal to micron sizes allows for tuning the energies of Rydberg excitons locally, and precisely, by optically induced temperature change. These results pave the way for exploiting the large nonlinearities of Rydberg excitons in micropillars for making non-classical light sources, while the precise tuning of their emission energy opens up a viable pathway for realising a scalable photonic quantum simulation platform.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title>
<jats:p>Rydberg excitons in Cu<jats:sub>2</jats:sub>O feature giant optical nonlinearities. To exploit these nonlinearities for quantum applications, the confinement must match the Rydberg blockade size, which in Cu<jats:sub>2</jats:sub>O could be as large as a few microns. Here, in a top-down approach, we show how exciton confinement can be realised by focused-ion-beam etching of a polished bulk Cu<jats:sub>2</jats:sub>O crystal without noticeable degradation of the excitonic properties. The etching of the crystal to micron sizes allows for tuning the energies of Rydberg excitons locally, and precisely, by optically induced temperature change. These results pave the way for exploiting the large nonlinearities of Rydberg excitons in micropillars for making non-classical light sources, while the precise tuning of their emission energy opens up a viable pathway for realising a scalable photonic quantum simulation platform.</jats:p>
<jats:p>Rydberg excitons in Cu<jats:sub>2</jats:sub>O feature giant optical nonlinearities. To exploit these nonlinearities for quantum applications, the confinement must match the Rydberg blockade size, which in Cu<jats:sub>2</jats:sub>O could be as large as a few microns. Here, in a top-down approach, we show how exciton confinement can be realised by focused-ion-beam etching of a polished bulk Cu<jats:sub>2</jats:sub>O crystal without noticeable degradation of the excitonic properties. The etching of the crystal to micron sizes allows for tuning the energies of Rydberg excitons locally, and precisely, by optically induced temperature change. These results pave the way for exploiting the large nonlinearities of Rydberg excitons in micropillars for making non-classical light sources, while the precise tuning of their emission energy opens up a viable pathway for realising a scalable photonic quantum simulation platform.</jats:p>
G. Bourcin; A. Gardin; J. Bourhill; V. Vlaminck; V. Castel
Level attraction in a quasiclosed cavity: Antiresonance in magnonic devices Journal Article
In: Phys. Rev. Applied, vol. 22, no. 6, 2024, ISSN: 2331-7019.
@article{Bourcin2024,
title = {Level attraction in a quasiclosed cavity: Antiresonance in magnonic devices},
author = {G. Bourcin and A. Gardin and J. Bourhill and V. Vlaminck and V. Castel},
doi = {10.1103/physrevapplied.22.064036},
issn = {2331-7019},
year = {2024},
date = {2024-12-00},
urldate = {2024-12-00},
journal = {Phys. Rev. Applied},
volume = {22},
number = {6},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}