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Journal articlePaige AJ, Kwon H, Simsek S, et al., 2020,
Quantum delocalized interactions
, Physical Review Letters, Vol: 125, Pages: 240406 – 1-240406 – 6, ISSN: 0031-9007Classical mechanics obeys the intuitive logic that a physical event happens at a definite spatial point. Entanglement, however, breaks this logic by enabling interactions without a specific location. In this work we study these delocalized interactions. These are quantum interactions that create less locational information than would be possible classically, as captured by the disturbance induced on some spatial superposition state. We introduce quantum games to capture the effect and demonstrate a direct operational use for quantum concurrence in that it bounds the nonclassical performance gain. We also find a connection with quantum teleportation, and demonstrate the games using an IBM quantum processor.
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Journal articleDrahi D, Walk N, Hoban MJ, et al., 2020,
Certified Quantum Random Numbers from Untrusted Light
, PHYSICAL REVIEW X, Vol: 10, ISSN: 2160-3308- Author Web Link
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- Citations: 27
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Journal articleEnzian G, Price J, Freisem L, et al., 2020,
Single-phonon addition and subtraction to a mechanical thermal state
, Physical Review Letters, ISSN: 0031-9007 -
Journal articleCaldwell L, Tarbutt MR, 2020,
Enhancing dipolar interactions between molecules using state-dependent optical tweezer traps
, Physical Review Letters, Vol: 125, Pages: 243201 – 1-243201 – 6, ISSN: 0031-9007We show how state-dependent optical potentials can be used to trap a pair of molecules in different internal states at a separation much smaller than the wavelength of the trapping light. This close spacing greatly enhances thedipole-dipole interaction and we show how it can be used to implement two-qubit gates between molecules that are 100 times faster than existing protocols and than rotational coherence times already demonstrated. We analyze complications due to hyperfine structure, tensor light shifts, photon scattering and collisional loss, and conclude that none is a barrier to implementing the scheme.
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Journal articleJia Z-A, Zhai R, Yu S, et al., 2020,
Hierarchy of genuine multipartite quantum correlations
, Quantum Information Processing, Vol: 19, ISSN: 1570-0755 -
Journal articleDhar HS, Rodrigues JD, Walker BT, et al., 2020,
Transport and localization of light inside a dye-filled microcavity
, Physical Review A: Atomic, Molecular and Optical Physics, Vol: 102, Pages: 1-9, ISSN: 1050-2947The driven-dissipative nature of light-matter interaction inside a multimode, dye-filled microcavity makes it an ideal system to study nonequilibrium phenomena, such as transport. In this work, we investigate how light is efficiently transported inside such a microcavity, mediated by incoherent absorption and emission processes. In particular, we show that there exist two distinct regimes of transport, viz. conductive and localized, arising from the complex interplay between the thermalizing effect of the dye molecules and the nonequilibrium influence of driving and loss. The propagation of light in the conductive regime occurs when several localized cavity modes undergo dynamical phase transitions to a condensed, or lasing, state. Furthermore, we observe that, while such transport is robust for weak disorder in the cavity potential, strong disorder can lead to localization of light even under good thermalizing conditions. Importantly, the exhibited transport and localization of light is a manifestation of the nonequilibrium dynamics rather than any coherent interference in the system.
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Journal articleOh C, Kwon H, Jiang L, et al., 2020,
Field-gradient measurement using a Stern-Gerlach atomic interferometer with butterfly geometry
, Physical Review A: Atomic, Molecular and Optical Physics, Vol: 102, Pages: 053321 – 1-053321 – 8, ISSN: 1050-2947Atomic interferometers have been studied as a promising device for precise sensing of external fields. Among various configurations, a particular configuration with a butterfly-shaped geometry has been designed to sensitively probe field gradients. We introduce a Stern-Gerlach (SG) butterfly interferometer by incorporating magnetic field in the conventional butterfly-shaped configuration. Atomic trajectories of the interferometer can be flexibly adjusted by controlling magnetic fields to increase the sensitivity of the interferometer, while the conventional butterfly interferometer using Raman transitions can be understood as a special case. We also show that the SG interferometer can keep high contrast against a misalignment in position and momentum caused by the field gradient.
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Journal articleJennings D, Cirstoiu C, Korzekwa K, 2020,
Robustness of Noether's principle: maximal disconnects between conservation laws and symmetries in quantum theory
, Physical Review X, Vol: 10, Pages: 041035 – 1-041035 – 41, ISSN: 2160-3308To what extent does Noether’s principle apply to quantum channels? Here, we quantify the degreeto which imposing a symmetry constraint on quantum channels implies a conservation law, and showthat this relates to physically impossible transformations in quantum theory, such as time-reversaland spin-inversion. In this analysis, the convex structure and extremal points of the set of quantumchannels symmetric under the action of a Lie group G becomes essential. It allows us to derivebounds on the deviation from conservation laws under any symmetric quantum channel in terms ofthe deviation from closed dynamics as measured by the unitarity of the channel E. In particular,we investigate in detail the U(1) and SU(2) symmetries related to energy and angular momentumconservation laws. In the latter case, we provide fundamental limits on how much a spin-jA systemcan be used to polarise a larger spin-jB system, and on how much one can invert spin polarisationusing a rotationally-symmetric operation. Finally, we also establish novel links between unitarity,complementary channels and purity that are of independent interest.
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Journal articleMukherjee R, Xie H, Mintert F, 2020,
Bayesian Optimal Control of Greenberger-Horne-Zeilinger States in Rydberg Lattices
, PHYSICAL REVIEW LETTERS, Vol: 125, ISSN: 0031-9007- Author Web Link
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- Citations: 20
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Journal articleWan KH, Neville A, Kolthammer WS, 2020,
Memory-assisted decoder for approximate Gottesman-Kitaev-Preskill codes
, Physical Review Research, Vol: 2, ISSN: 2643-1564We propose a quantum error correction protocol for continuous-variable finite-energy, approximate Gottesman-Kitaev-Preskill (GKP) states undergoing small Gaussian random displacement errors, based on the scheme of Glancy and Knill [Phys. Rev. A 73, 012325 (2006)]. We show that combining multiple rounds of error-syndrome extraction with Bayesian estimation offers enhanced protection of GKP-encoded qubits over comparible single-round approaches. Furthermore, we show that the expected total displacement error incurred in multiple rounds of error followed by syndrome extraction is bounded by 2√π. By recompiling the syndrome-extraction circuits, we show that all squeezing operations can be subsumed into auxiliary state preparation, reducing them to beamsplitter transformations and quadrature measurements.
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Journal articleHolmes Z, Mintert F, Anders J, 2020,
Gibbs mixing of partially distinguishable photons with a polarising beamsplitter membrane
, NEW JOURNAL OF PHYSICS, Vol: 22, ISSN: 1367-2630- Author Web Link
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- Citations: 2
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Journal articleMeng Y, Yu S, Jia Z-A, et al., 2020,
Environment-induced sudden change of coherence in quantum systems
, PHYSICAL REVIEW A, Vol: 102, ISSN: 2469-9926- Author Web Link
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- Citations: 6
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Journal articleBurdekin P, Grandi S, Newbold R, et al., 2020,
Single-Photon-Level Sub-Doppler Pump-Probe Spectroscopy of Rubidium
, PHYSICAL REVIEW APPLIED, Vol: 14, ISSN: 2331-7019 -
Journal articleThekkadath GS, Mycroft ME, Bell BA, et al., 2020,
Quantum-enhanced interferometry with large heralded photon-number states
, NPJ QUANTUM INFORMATION, Vol: 6- Author Web Link
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- Citations: 23
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Journal articleTardiff E, Fan X, Gabrielse G, et al., 2020,
Two-symmetry Penning-Ioffe trap for antihydrogen cooling and spectroscopy
, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol: 977, Pages: 1-17, ISSN: 0168-9002High-accuracy spectroscopic comparisons of trapped antihydrogen atoms (H) and hydrogen atoms (H) promiseto stringently test the fundamental CPT symmetry invariance of the standard model of particle physics. ATRAP’snested Penning-Ioffe trap was developed for such studies. The first of its unique features is that its magneticIoffe trap forHatoms can be switched between quadrupole and octupole symmetries. The second is that itallows laser and microwave access perpendicular to the central axis of the traps.
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Journal articleXie J, Zhang A, Cao N, et al., 2020,
Observing Geometry of Quantum States in a Three-Level System
, Physical Review Letters, Vol: 125, ISSN: 0031-9007 -
Journal articleNehra R, Eaton M, Gonzalez-Arciniegas C, et al., 2020,
Generalized overlap quantum state tomography
, PHYSICAL REVIEW RESEARCH, Vol: 2- Author Web Link
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- Citations: 6
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Journal articleDriver T, Cooper B, Ayers R, et al., 2020,
Two-dimensional partial covariance mass spectrometry of large molecules based on fragment correlations
, Physical Review X, Vol: 10, Pages: 041004 – 1-041004 – 13, ISSN: 2160-3308Covariance mapping [L. J. Frasinski, K. Codling, and P. A. Hatherly, Science 246, 1029 (1989)] is a well-established technique used for the study of mechanisms of laser-induced molecular ionization and decomposition. It measures statistical correlations between fluctuating signals of pairs of detected species (ions, fragments, electrons). A positive correlation identifies pairs of products originating from the same dissociation or ionization event. A major challenge for covariance-mapping spectroscopy is accessing decompositions of large polyatomic molecules, where true physical correlations are overwhelmed by spurious signals of no physical significance induced by fluctuations in experimental parameters. As a result, successful applications of covariance mapping have so far been restricted to low-mass systems, e.g., organic molecules of around 50 daltons (Da). Partial-covariance mapping was suggested to tackle the problem of spurious correlations by taking into account the independently measured fluctuations in the experimental conditions. However, its potential has never been realized for the decomposition of large molecules, because in these complex situations, determining and continuously monitoring multiple experimental parameters affecting all the measured signals simultaneously becomes unfeasible. We introduce, through deriving theoretically and confirming experimentally, a conceptually new type of partial-covariance mapping—self-correcting partial-covariance spectroscopy—based on a parameter extracted from the measured spectrum itself. We use the readily available total ion count as the self-correcting partial-covariance parameter, thus eliminating the challenge of determining experimental parameter fluctuations in covariance measurements of large complex systems. The introduced self-correcting partial covariance enables us to successfully resolve correlations of molecules as large as
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Journal articleLiu W, Wang Y-T, Li Z-P, et al., 2020,
An ultrastable and robust single-photon emitter in hexagonal boron nitride
, Physica E: Low-dimensional Systems and Nanostructures, Vol: 124, Pages: 114251-114251, ISSN: 1386-9477 -
Journal articleKhokhlova M, Bahmanpour L, Bachhawat N, et al., 2020,
Interatomic coulombic decay rate in endohedral complexes
, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 53, ISSN: 0953-4075 -
Journal articleKuroś A, Mukherjee R, Golletz W, et al., 2020,
Phase diagram and optimal control for n-tupling discrete time crystal
, New Journal of Physics, Vol: 22, Pages: 1-13, ISSN: 1367-2630 -
Journal articleKwon H, Paige AJ, Kim MS, 2020,
Condition on the Rényi entanglement entropy under stochastic local manipulation
, Physical Review Letters, Vol: 125, Pages: 100502 – 1-100502 – 7, ISSN: 0031-9007The Rényi entanglement entropy (REE) is an entanglement quantifier considered as a natural generalization of the entanglement entropy. When it comes to stochastic local operations and classical communication (SLOCC), however, only a limited class of the REEs satisfy the monotonicity condition, while their statistical properties beyond mean values have not been fully investigated. Here, we establish a general condition that the probability distribution of the REE of any order obeys under SLOCC. The condition is obtained by introducing a family of entanglement monotones that contain the higher-order moments of the REEs. The contribution from the higher-order moments imposes a strict limitation on entanglement distillation via SLOCC. We find that the upper bound on success probabilities for entanglement distillation exponentially decreases as the amount of raised entanglement increases, which cannot be captured from the monotonicity of the REE. Based on the strong restriction on entanglement transformation under SLOCC, we design a new method to estimate entanglement in quantum many-body systems from experimentally observable quantities.
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Journal articleHunter-Gordon M, Szabo Z, Nyman RA, et al., 2020,
Quantum simulation of the dephasing Anderson model
, Physical Review A: Atomic, Molecular and Optical Physics, Vol: 102, Pages: 022407 – 1-022407 – 4, ISSN: 1050-2947The interplay of Anderson localization and decoherence results in intricate dynamics that is notoriously difficult to simulate on classical computers. We develop the framework for a quantum simulation of such an open quantum system making use of time-varying randomized gradients, and show that even an implementation with limited experimental resources results in accurate simulations.
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Journal articleO'Neal JT, Champenois EG, Oberli S, et al., 2020,
Electronic Population Transfer via Impulsive Stimulated X-Ray Raman Scattering with Attosecond Soft-X-Ray Pulses
, PHYSICAL REVIEW LETTERS, Vol: 125, ISSN: 0031-9007- Author Web Link
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- Citations: 30
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Journal articleYu S, Meng Y, Patel RB, et al., 2020,
Experimental Observation of Coherent-Information Superadditivity in a Dephrasure Channel
, PHYSICAL REVIEW LETTERS, Vol: 125, ISSN: 0031-9007- Author Web Link
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- Citations: 5
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Journal articleWeaver B, Greening D, Tisch J, et al., 2020,
Generation and measurement of isolated attosecond pulses with enhanced flux using a two colour synthesized laser field
, Optics Express, Vol: 28, Pages: 23329-23337, ISSN: 1094-4087We have generated isolated attosecond pulses and performed attosecond streaking measurements using a two-colour synthesized laser field consisting of a strong near-infrared few-cycle pulse and a weaker multi-cycle pulse centred at 400 nm. An actively stabilized interferometer was used to coherently combine the two pulses. Using attosecond streaking we characterised the electric fields of the two pulses and accurately retrieved the spectrum of the multi-cycle pulse. We demonstrated a two-fold increase in the flux of isolated attosecond pulses produced and show that their duration was minimally affected by the presence of the weaker field due to spectral filtering by a multilayer mirror.
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Journal articleKe Z-J, Wang Y-T, Yu S, et al., 2020,
Detection and quantification of entanglement with measurement-device-independent and universal entanglement witness*
, Chinese Physics B, Vol: 29, Pages: 080301-080301, ISSN: 1674-1056<jats:p>Entanglement is the key resource in quantum information processing, and an entanglement witness (EW) is designed to detect whether a quantum system has any entanglement. However, prior knowledge of the target states should be known first to design a suitable EW, which weakens this method. Nevertheless, a recent theory shows that it is possible to design a universal entanglement witness (UEW) to detect negative-partial-transpose (NPT) entanglement in unknown bipartite states with measurement-device-independent (MDI) characteristic. The outcome of a UEW can also be upgraded to be an entanglement measure. In this study, we experimentally design and realize an MDI UEW for two-qubit entangled states. All of the tested states are well-detected without any prior knowledge. We also show that it is able to quantify entanglement by comparing it with concurrence estimated through state tomography. The relation between them is also revealed. The entire experimental framework ensures that the UEW is MDI.</jats:p>
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Journal articleCrespo H, Witting T, Canhota M, et al., 2020,
In-situ temporal measurement of ultrashort laser pulses at full power during high-intensity laser-matter interactions
, Optica, Vol: 7, Pages: 995-1002, ISSN: 2334-2536In laser-matter interaction experiments it is of paramount importance to be able tocharacterise the laser pulse on target (in-situ) and at full power. This allows pulse optimisationand meaningful comparison with theory, and can shed fundamental new light on pulse distortionsoccurring in or on the target. Here we introduce and demonstrate a new technique based ondispersion scan using the concurrent third harmonic emission from the target that permits the full(amplitude and phase), in-situ, in-parallel characterisation of ultrashort laser pulses in a gas orsolid target over a very wide intensity range that encompasses the1013−1015W cm−2regime ofhigh harmonic generation and other important strong field phenomena, with possible extensionto relativistic intensities also presently inaccessible to other diagnostics.
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Journal articleMa Y, Khosla K, Stickler B, et al., 2020,
Quantum persistent tennis racket dynamics of nanorotors
, Physical Review Letters, Vol: 125, ISSN: 0031-9007Classical rotations of asymmetric rigid bodies are unstable around the axis of intermediate moment of inertia, causing a flipping of rotor orientation. This effect, known as the tennis racket effect, quickly averages to zero in classical ensembles since the flipping period varies significantly upon approaching the separatrix. Here, we explore the quantum rotations of rapidly spinning thermal asymmetric nanorotors and show that classically forbidden tunnelling gives rise to persistent tennis racket dynamics, in stark contrast to the classical expectation. We characterise this effect, demonstrating that quantum coherent flipping dynamics can persist even in the regime where millions of angular momentum states are occupied. This persistent flipping offers a promising route for observing and exploiting quantum effects in rotational degrees of freedom for molecules and nanoparticles.
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Journal articleMeng C, Brawley GA, Bennett JS, et al., 2020,
Mechanical Squeezing via Fast Continuous Measurement
, PHYSICAL REVIEW LETTERS, Vol: 125, ISSN: 0031-9007- Author Web Link
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- Citations: 19
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