ORCID Profile
0000-0002-4714-0575
Current Organisations
University of Oxford
,
Imperial Colllege London
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Publisher: Springer Science and Business Media LLC
Date: 07-05-2013
DOI: 10.1038/SREP01779
Publisher: Springer Science and Business Media LLC
Date: 23-10-2020
DOI: 10.1038/S41534-020-00320-Y
Abstract: Quantum phenomena such as entanglement can improve fundamental limits on the sensitivity of a measurement probe. In optical interferometry, a probe consisting of N entangled photons provides up to a $$\\sqrt{N}$$ N enhancement in phase sensitivity compared to a classical probe of the same energy. Here, we employ high-gain parametric down-conversion sources and photon-number-resolving detectors to perform interferometry with heralded quantum probes of sizes up to N = 8 (i.e. measuring up to 16-photon coincidences). Our probes are created by injecting heralded photon-number states into an interferometer, and in principle provide quantum-enhanced phase sensitivity even in the presence of significant optical loss. Our work paves the way toward quantum-enhanced interferometry using large entangled photonic states.
Publisher: American Physical Society (APS)
Date: 25-04-2013
Publisher: Springer Science and Business Media LLC
Date: 15-01-2013
DOI: 10.1038/NCOMMS2349
Abstract: Increasing the complexity of quantum photonic devices is essential for many optical information processing applications to reach a regime beyond what can be classically simulated, and integrated photonics has emerged as a leading platform for achieving this. Here we demonstrate three-photon quantum operation of an integrated device containing three coupled interferometers, eight spatial modes and many classical and nonclassical interferences. This represents a critical advance over previous complexities and the first on-chip nonclassical interference with more than two photonic inputs. We introduce a new scheme to verify quantum behaviour, using classically characterised device elements and hierarchies of photon correlation functions. We accurately predict the device's quantum behaviour and show operation inconsistent with both classical and bi-separable quantum models. Such methods for verifying multiphoton quantum behaviour are vital for achieving increased circuit complexity. Our experiment paves the way for the next generation of integrated photonic quantum simulation and computing devices.
Publisher: American Physical Society (APS)
Date: 10-01-2022
Publisher: The Optical Society
Date: 16-10-2014
DOI: 10.1364/OL.39.006090
Publisher: The Optical Society
Date: 06-09-2018
DOI: 10.1364/OE.26.024678
Publisher: Springer Science and Business Media LLC
Date: 27-11-2014
DOI: 10.1038/NCOMMS6584
Abstract: Quantum properties of optical modes are typically assessed by observing their photon statistics or the distribution of their quadratures. Both particle- and wave-like behaviours deliver important information and each may be used as a resource in quantum-enhanced technologies. Weak-field homodyne (WFH) detection provides a scheme that combines the wave- and particle-like descriptions. Here we show that it is possible to observe a wave-like property such as the optical coherence across Fock basis states in the detection statistics derived from discrete photon counting. We experimentally demonstrate these correlations using two WHF detectors on each mode of two classes of two-mode entangled states. Furthermore, we theoretically describe the response of WHF detection on a two-mode squeezed state in the context of generalized Bell inequalities. Our work demonstrates the potential of this technique as a tool for hybrid continuous/discrete-variable protocols on a phenomenon that explicitly combines both approaches.
Publisher: SPIE
Date: 03-03-2022
DOI: 10.1117/12.2616725
Publisher: American Physical Society (APS)
Date: 30-09-2022
Publisher: The Optical Society
Date: 31-10-2017
DOI: 10.1364/OE.25.028236
Publisher: AIP Publishing
Date: 13-07-2020
DOI: 10.1063/5.0009681
Abstract: Nonlinear optical microscopy techniques have emerged as a set of successful tools for biological imaging. Stimulated emission microscopy belongs to a small subset of pump–probe techniques, which can image non-fluorescent s les without requiring fluorescent labeling. However, its sensitivity has been shown to be ultimately limited by the quantum fluctuations in the probe beam. We propose and experimentally implement sub-shot-noise limited stimulated emission microscopy by preparing the probe pulse in an intensity-squeezed state. This technique paves the way for imaging delicate biological s les that have no detectable fluorescence with sensitivity beyond standard quantum fluctuations.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 20-12-2012
Abstract: Although universal quantum computers ideally solve problems such as factoring integers exponentially more efficiently than classical machines, the formidable challenges in building such devices motivate the demonstration of simpler, problem-specific algorithms that still promise a quantum speedup. We constructed a quantum boson-s ling machine (QBSM) to s le the output distribution resulting from the nonclassical interference of photons in an integrated photonic circuit, a problem thought to be exponentially hard to solve classically. Unlike universal quantum computation, boson s ling merely requires indistinguishable photons, linear state evolution, and detectors. We benchmarked our QBSM with three and four photons and analyzed sources of s ling inaccuracy. Scaling up to larger devices could offer the first definitive quantum-enhanced computation.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 28-01-2022
Abstract: Identifying the boundary beyond which quantum machines provide a computational advantage over their classical counterparts is a crucial step in charting their usefulness. Gaussian boson s ling (GBS), in which photons are measured from a highly entangled Gaussian state, is a leading approach in pursuing quantum advantage. State-of-the-art GBS experiments that run in minutes would require 600 million years to simulate using the best preexisting classical algorithms. Here, we present faster classical GBS simulation methods, including speed and accuracy improvements to the calculation of loop hafnians. We test these on a ∼100,000-core supercomputer to emulate GBS experiments with up to 100 modes and up to 92 photons. This reduces the simulation time for state-of-the-art GBS experiments to several months, a nine–orders of magnitude improvement over previous estimates. Last, we introduce a distribution that is efficient to s le from classically and that passes a variety of GBS validation methods.
Publisher: The Optical Society
Date: 29-05-2013
DOI: 10.1364/OE.21.013522
Publisher: Springer Science and Business Media LLC
Date: 14-09-2014
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8DT00864G
Abstract: We report on the synthesis, crystal structures, optoelectronic properties and solar cell device studies of three novel hybrid bismuth-halide materials as lead-free light harvesters.
Publisher: Optica Publishing Group
Date: 14-01-2022
DOI: 10.1364/OE.450172
Abstract: Multiphoton contributions pose a significant challenge for the realisation of heralded single-photon sources (HSPS) based on nonlinear processes. In this work, we improve the quality of single photons generated in this way by harnessing the photon-number resolving (PNR) capabilities of commercial superconducting nanowire single-photon detectors (SNSPDs). We report a 13 ± 0.4% reduction of g (2) ( τ = 0), even with a collection efficiency in the photon source of only 29.6%. Our work demonstrates the first application of the PNR capabilities of SNSPDs and shows improvement in the quality of an HSPS with widely available technology.
Publisher: American Physical Society (APS)
Date: 09-12-2020
Publisher: American Physical Society (APS)
Date: 17-05-2022
Publisher: American Physical Society (APS)
Date: 15-08-2013
Publisher: Wiley
Date: 16-12-2008
Publisher: Springer Science and Business Media LLC
Date: 10-2009
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7DT00752C
Abstract: Coordination compounds of the type [M II (L˙) 2 ][Re IV X 6 ] display a variety of different intra- and inter-molecular magnetic interactions.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 2016
Abstract: Control of a two-photon quantum walk in a complex multimode system by wavefront shaping.
Publisher: Springer Science and Business Media LLC
Date: 14-04-2014
DOI: 10.1038/NCOMMS4532
Abstract: Phase estimation, at the heart of many quantum metrology and communication schemes, can be strongly affected by noise, whose litude may not be known, or might be subject to drift. Here we investigate the joint estimation of a phase shift and the litude of phase diffusion at the quantum limit. For several relevant instances, this multiparameter estimation problem can be effectively reshaped as a two-dimensional Hilbert space model, encompassing the description of an interferometer phase probed with relevant quantum states--split single-photons, coherent states or N00N states. For these cases, we obtain a trade-off bound on the statistical variances for the joint estimation of phase and phase diffusion, as well as optimum measurement schemes. We use this bound to quantify the effectiveness of an actual experimental set-up for joint parameter estimation for polarimetry. We conclude by discussing the form of the trade-off relations for more general states and measurements.
Publisher: American Physical Society (APS)
Date: 27-02-2014
Publisher: The Optical Society
Date: 31-08-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0SC03229H
Abstract: In situ high-pressure single-crystal diffraction and spectroscopic techniques have been used to study a previously unreported Cu-framework bis[1-(4-pyridyl)butane-1,3-dione]copper( ii ) (CuPyr-I).
Publisher: Elsevier BV
Date: 11-2007
Publisher: Springer Science and Business Media LLC
Date: 07-2023
DOI: 10.1038/S41467-023-38413-9
Abstract: One of the core questions of quantum physics is how to reconcile the unitary evolution of quantum states, which is information-preserving and time-reversible, with evolution following the second law of thermodynamics, which, in general, is neither. The resolution to this paradox is to recognize that global unitary evolution of a multi-partite quantum state causes the state of local subsystems to evolve towards maximum-entropy states. In this work, we experimentally demonstrate this effect in linear quantum optics by simultaneously showing the convergence of local quantum states to a generalized Gibbs ensemble constituting a maximum-entropy state under precisely controlled conditions, while introducing an efficient certification method to demonstrate that the state retains global purity. Our quantum states are manipulated by a programmable integrated quantum photonic processor, which simulates arbitrary non-interacting Hamiltonians, demonstrating the universality of this phenomenon. Our results show the potential of photonic devices for quantum simulations involving non-Gaussian states.
Publisher: American Physical Society (APS)
Date: 29-09-2017
Publisher: Springer Science and Business Media LLC
Date: 12-10-2023
Publisher: Optica Publishing Group
Date: 17-05-2021
DOI: 10.1364/OL.421646
Abstract: The discrimination of coherent states is a key task in optical communication and quantum key distribution protocols. In this work, we use a photon-number-resolving detector, the transition-edge sensor, to discriminate binary-phase-shifted coherent states at a telecom wavelength. Owing to its dynamic range and high efficiency, we achieve a bit error probability that unconditionally exceeds the standard quantum limit (SQL) by up to 7.7 dB. The improvement to the SQL persists for signals containing up to approximately seven photons on average and is achieved in a single shot (i.e., without measurement feedback), thus making our approach compatible with larger bandwidths.
Publisher: American Physical Society (APS)
Date: 02-2016
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Ian Walmsley.