scholarly journals Reduced spin measurement back-action for a phase sensitivity ten times beyond the standard quantum limit

2014 ◽  
Vol 8 (9) ◽  
pp. 731-736 ◽  
Author(s):  
J. G. Bohnet ◽  
K. C. Cox ◽  
M. A. Norcia ◽  
J. M. Weiner ◽  
Z. Chen ◽  
...  
Keyword(s):  
Quantum Limit ◽  
Phase Sensitivity ◽  
Standard Quantum ◽  
Standard Quantum Limit ◽  
Back Action

scholarly journals Beating the standard quantum limit under ambient conditions with solid-state spins

2021 ◽  
Vol 7 (32) ◽  
pp. eabg9204
Author(s):  
Tianyu Xie ◽  
Zhiyuan Zhao ◽  
Xi Kong ◽  
Wenchao Ma ◽  
Mengqi Wang ◽  
...  
Keyword(s):  
Solid State ◽  
Nitrogen Vacancy ◽  
Quantum Limit ◽  
Phase Sensitivity ◽  
Ambient Conditions ◽  
Nuclear Spins ◽  
Standard Quantum ◽  
Standard Quantum Limit ◽  
Negative State ◽  
State Spin

The use of entangled sensors improves the precision limit from the standard quantum limit (SQL) to the Heisenberg limit. Most previous experiments beating the SQL are performed on the sensors that are well isolated under extreme conditions. Here, we demonstrate a sub-SQL interferometer at ambient conditions by using a multispin system, namely, the nitrogen-vacancy (NV) defect in diamond. We achieve two-spin interference with a phase sensitivity of 1.79 ± 0.06 dB beyond the SQL and three-spin interference with a phase sensitivity of 2.77 ± 0.10 dB. Besides, a magnetic sensitivity of 0.87 ± 0.09 dB beyond the SQL is achieved by two-spin interference for detecting a real magnetic field. Particularly, the deterministic and joint initialization of NV negative state, NV electron spin, and two nuclear spins is realized at room temperature. The techniques used here are of fundamental importance for quantum sensing and computing, and naturally applicable to other solid-state spin systems.

Quantum measurement

Quantum 20/20 ◽  
2019 ◽  
pp. 181-200
Author(s):  
Ian R. Kenyon
Keyword(s):  
Gravitational Waves ◽  
Quantum Measurement ◽  
Input Port ◽  
Quantum Limit ◽  
Photon Flux ◽  
Standard Quantum ◽  
Standard Quantum Limit ◽  
Back Action

Heisenberg’s back action and Robertson’s intrinsic uncertainty are presented. von Neumann’s analysis of quantum measurement is recounted. Advanced LIGO is used as an example of quantum measurement: giant Michelson interferometers achieve sensitivity to motion of 1 part in 1021. The discovery at LIGO of gravitational waves is outlined. Then the standard quantum limit is deduced. The use of cavities in the interferometer arms to increase the photon flux is described. The potential for improvement by squeezing the vacuum at the blank input port is discussed. Prospects for speed interferometry are outlined.

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.

scholarly journals The standard quantum limit of coherent beam combining

2019 ◽  
Vol 21 (9) ◽  
pp. 093047 ◽  
Author(s):  
C R Müller ◽  
F Sedlmeir ◽  
V O Martynov ◽  
Ch Marquardt ◽  
A V Andrianov ◽  
...  
Keyword(s):  
Coherent Beam ◽  
Quantum Limit ◽  
Standard Quantum ◽  
Standard Quantum Limit ◽  
Coherent Beam Combining ◽  
Beam Combining
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