scholarly journals Beating the classical precision limit with spin-1 Dicke states of more than 10,000 atoms

2018 ◽  
Vol 115 (25) ◽  
pp. 6381-6385 ◽  
Author(s):  
Yi-Quan Zou ◽  
Ling-Na Wu ◽  
Qi Liu ◽  
Xin-Yu Luo ◽  
Shuai-Feng Guo ◽  
...  
Keyword(s):  
Laser Interferometer ◽  
Precision Measurements ◽  
Quantum Limit ◽  
Quantum Metrology ◽  
Standard Quantum ◽  
Standard Quantum Limit ◽  
Precision Limit ◽  
Individual Particles ◽  
Entangled Atoms ◽  
Dicke States

Interferometry is a paradigm for most precision measurements. Using N uncorrelated particles, the achievable precision for a two-mode (two-path) interferometer is bounded by the standard quantum limit (SQL), 1/N, due to the discrete (quanta) nature of individual measurements. Despite being a challenging benchmark, the two-mode SQL has been approached in a number of systems, including the Laser Interferometer Gravitational-Wave Observatory and today’s best atomic clocks. For multimode interferometry, the SQL becomes 1/[(M−1)N] using M modes. Higher precision can also be achieved using entangled particles such that quantum noises from individual particles cancel out. In this work, we demonstrate an interferometric precision of 2.42−1.29+1.76 dB beyond the three-mode SQL, using balanced spin-1 (three-mode) Dicke states containing thousands of entangled atoms. The input quantum states are deterministically generated by controlled quantum phase transition and exhibit close to ideal quality. Our work shines light on the pursuit of quantum metrology beyond SQL.

scholarly journals Mesoscopic atomic entanglement for precision measurements beyond the standard quantum limit

2009 ◽  
Vol 106 (27) ◽  
pp. 10960-10965 ◽  
Author(s):  
J. Appel ◽  
P. J. Windpassinger ◽  
D. Oblak ◽  
U. B. Hoff ◽  
N. Kjaergaard ◽  
...  
Keyword(s):  
Precision Measurements ◽  
Quantum Limit ◽  
Standard Quantum ◽  
Standard Quantum Limit ◽  
Atomic Entanglement

scholarly journals Machine Learning for Quantum Metrology

Proceedings ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 28
Author(s):  
Nicolò Spagnolo ◽  
Alessandro Lumino ◽  
Emanuele Polino ◽  
Adil S. Rab ◽  
Nathan Wiebe ◽  
...  
Keyword(s):  
Machine Learning ◽  
Single Photon ◽  
Quantum Limit ◽  
Physical Parameters ◽  
Phase Estimation ◽  
Quantum Metrology ◽  
Standard Quantum ◽  
Asymptotically Optimal ◽  
Standard Quantum Limit ◽  
Optimal Machine

Phase estimation represents a significant example to test the application of quantum theory for enhanced measurements of unknown physical parameters. Several recipes have been developed, allowing to define strategies to reach the ultimate bounds in the asymptotic limit of a large number of trials. However, in certain applications it is crucial to reach such bound when only a small number of probes is employed. Here, we discuss an asymptotically optimal, machine learning based, adaptive single-photon phase estimation protocol that allows us to reach the standard quantum limit when a very limited number of photons is employed.

scholarly journals Restoring Heisenberg scaling in noisy quantum metrology by monitoring the environment

Quantum ◽  
2018 ◽  
Vol 2 ◽  
pp. 110 ◽  
Author(s):  
Francesco Albarelli ◽  
Matteo A. C. Rossi ◽  
Dario Tamascelli ◽  
Marco G. Genoni
Keyword(s):  
Detection Efficiency ◽  
Frequency Estimation ◽  
Quantum Fisher Information ◽  
Quantum Limit ◽  
Convexity Property ◽  
Quantum Metrology ◽  
Standard Quantum ◽  
Standard Quantum Limit ◽  
Photo Detection ◽  
Continuous Estimation

We study quantum frequency estimation for N qubits subjected to independent Markovian noise, via strategies based on time-continuous monitoring of the environment. Both physical intuition and an extended convexity property of the quantum Fisher information (QFI) suggest that these strategies are more effective than the standard ones based on the measurement of the unconditional state after the noisy evolution. Here we focus on initial GHZ states and on parallel or transverse noise. For parallel noise, i.e. dephasing, we show that perfectly efficient time-continuous photo-detection allows to recover the unitary (noiseless) QFI, and thus to obtain a Heisenberg scaling for every value of the monitoring time. For finite detection efficiency, one falls back to the noisy standard quantum limit scaling, but with a constant enhancement due to an effective reduced dephasing. Also in the transverse noise case we obtain that the Heisenberg scaling is recovered for perfectly efficient detectors, and we find that both homodyne and photo-detection based strategies are optimal. For finite detectors efficiency, our numerical simulations show that, as expected, an enhancement can be observed, but we cannot give any conclusive statement regarding the scaling. We finally describe in detail the stable and compact numerical algorithm that we have developed in order to evaluate the precision of such time-continuous estimation strategies, and that may find application in other quantum metrology schemes.

scholarly journals Entanglement-enhanced matter-wave interferometry in a high-finesse cavity

2021 ◽  
Author(s):  
James Thompson ◽  
Graham Greve ◽  
Chengyi Luo ◽  
Baochen Wu
Keyword(s):  
Cavity Qed ◽  
Degrees Of Freedom ◽  
Inertial Sensors ◽  
Mean Field ◽  
New Physics ◽  
Matter Wave ◽  
Quantum Limit ◽  
Entangled State ◽  
Standard Quantum ◽  
Standard Quantum Limit

Abstract Entanglement is a fundamental resource that allows quantum sensors to surpass the standard quantum limit set by the quantum collapse of independent atoms. Collective cavity-QED systems have succeeded in generating large amounts of directly observed entanglement involving the internal degrees of freedom of laser-cooled atomic ensembles. Here we demonstrate cavity-QED entanglement of external degrees of freedom to realize a matter-wave interferometer of 700 atoms in which each individual atom falls freely under gravity and simultaneously traverses two paths through space while also entangled with the other atoms. We demonstrate both quantum non-demolition measurements and cavity-mediated spin interactions for generating squeezed momentum states with directly observed metrological gain 3.4^{+1.1}_{-0.9} dB and 2.5^{+0.6}_{-0.6} dB below the standard quantum limit respectively. An entangled state is for the first time successfully injected into a Mach-Zehnder light-pulse interferometer with 1.7^{+0.5}_{-0.5} dB of directly observed metrological enhancement. These results open a new path for combining particle delocalization and entanglement for inertial sensors, searches for new physics, particles, and fields, future advanced gravitational wave detectors, and accessing beyond mean-field quantum many-body physics.

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