scholarly journals Proposal for a continuous wave laser with linewidth well below the standard quantum limit

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chenxu Liu ◽  
Maria Mucci ◽  
Xi Cao ◽  
M. V. Gurudev Dutt ◽  
Michael Hatridge ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Laser Cavity ◽  
Gain Medium ◽  
Low Noise ◽  
Quantum Limit ◽  
Continuous Wave Laser ◽  
Standard Quantum ◽  
Standard Quantum Limit ◽  
Superconducting Circuit ◽  
High Coherence

AbstractDue to their high coherence, lasers are ubiquitous tools in science. We show that by engineering the coupling between the gain medium and the laser cavity as well as the laser cavity and the output port, it is possible to eliminate most of the noise due to photons entering as well as leaving the laser cavity. Hence, it is possible to reduce the laser linewidth by a factor equal to the number of photons in the laser cavity below the standard quantum limit. We design and theoretically analyze a superconducting circuit that uses Josephson junctions, capacitors and inductors to implement a microwave laser, including the low-noise couplers that allow the design to surpass the standard quantum limit. Our proposal relies on the elements of superconducting quantum information, and thus is an example of how quantum engineering techniques can inspire us to re-imagine the limits of conventional quantum systems.

scholarly journals Beyond the standard quantum limit for parametric amplification of broadband signals

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
M. Renger ◽  
S. Pogorzalek ◽  
Q. Chen ◽  
Y. Nojiri ◽  
K. Inomata ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Quantum Information Processing ◽  
Low Noise ◽  
Parametric Amplification ◽  
Quantum Limit ◽  
Standard Quantum ◽  
Standard Quantum Limit ◽  
Input Noise ◽  
Microwave Signals ◽  
Maximum Quantum Efficiency

AbstractThe low-noise amplification of weak microwave signals is crucial for countless protocols in quantum information processing. Quantum mechanics sets an ultimate lower limit of half a photon to the added input noise for phase-preserving amplification of narrowband signals, also known as the standard quantum limit (SQL). This limit, which is equivalent to a maximum quantum efficiency of 0.5, can be overcome by employing nondegenerate parametric amplification of broadband signals. We show that, in principle, a maximum quantum efficiency of unity can be reached. Experimentally, we find a quantum efficiency of 0.69 ± 0.02, well beyond the SQL, by employing a flux-driven Josephson parametric amplifier and broadband thermal signals. We expect that our results allow for fundamental improvements in the detection of ultraweak microwave signals.

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

scholarly journals Squeezed-light-driven force detection with an optomechanical cavity in a Mach–Zehnder interferometer

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Chang-Woo Lee ◽  
Jae Hoon Lee ◽  
Hyojun Seok
Keyword(s):  
Zehnder Interferometer ◽  
Vacuum Field ◽  
Quantum Limit ◽  
Measurement Sensitivity ◽  
Force Detection ◽  
Detection Scheme ◽  
Standard Quantum ◽  
Standard Quantum Limit ◽  
Optomechanical Cavity ◽  
Mach Zehnder Interferometer

Abstract We analyze the performance of a force detector based on balanced measurements with a Mach–Zehnder interferometer incorporating a standard optomechanical cavity. The system is driven by a coherent superposition of coherent light and squeezed vacuum field, providing quantum correlation along with optical coherence in order to enhance the measurement sensitivity beyond the standard quantum limit. We analytically find the optimal measurement strength, squeezing direction, and squeezing strength at which the symmetrized power spectral density for the measurement noise is minimized below the standard quantum limit. This force detection scheme based on a balanced Mach–Zehnder interferometer provides better sensitivity compared to that based on balanced homodyne detection with a local oscillator in the low frequency regime.

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