High precision interferometers are the building blocks of precision metrology and the ultimate interferometric sensitivity is limited by the quantum noise. Here, we propose and experimentally demonstrate a compact quantum interferometer involving two optical parametric amplifiers and the squeezed states generated within the interferometer are directly used for the phase-sensing quantum state. By both squeezing shot noise and amplifying phase-sensing intensity the sensitivity improvement of 4.86±0.24 dB beyond the standard quantum limit is deterministically realized and a minimum detectable phase smaller than that of all present interferometers under the same phase-sensing intensity is achieved. This interferometric system has significantly potential applications in a variety of measurements for tiny variances of physical quantities.High precision interferometers are the building blocks of precision metrology and the ultimate interferometric sensitivity is limited by the quantum noise. Here, we propose and experimentally demonstrate a compact quantum interferometer involving two optical parametric amplifiers and the squeezed states generated within the interferometer are directly used for the phase-sensing quantum state. By both squeezing shot noise and amplifying phase-sensing intensity the sensitivity improvement of 4.86±0.24 dB beyond the standard quantum limit is deterministically realized and a minimum detectable phase smaller than that of all present interferometers under the same phase-sensing intensity is achieved. This interferometric system has significantly potential applications in a variety of measurements for tiny variances of physical quantities.

arXiv:2005.01911Physical Review LettersMay 1, 202078 citations

Squeezed Light in an Interferometer

Ray LaPierre

Undergraduate texts in physicsJan 1, 20220 citations

Distributed quantum sensing with squeezed-vacuum light in a configurable array of Mach-Zehnder interferometers

Marco Malitesta, Augusto Smerzi, Luca Pezzè

We study an entangled distributed quantum sensing scheme based on an array of $d$ Mach-Zehnder interferometers (MZIs) for the estimation of relative phase shifts. The scheme uses $d$ coherent states and a single squeezed-vacuum state that is distributed among the MZIs by a quantum circuit (QC). The protocol can be optimized analytically: it overcomes the shot-noise limit and reaches the Heisenberg limit with respect to the average total number of probe particles, ${\overline{n}}_{T}$ , for the estimation of arbitrary linear combinations of the $d$ phases. We compare the entangled strategy with a separable one that uses $d$ coherent and $d$ squeezed-vacuum states and the same ${\overline{n}}_{T}$ . The entangled strategy benefits for a substantial reduction of resource overhead and can achieve a maximum gain equal to $d$ when using the same total squeezed-light intensity as the separable strategy. Interestingly, the entangled strategy using a single squeezed-vacuum state can reach the same sensitivity as the separable strategy that uses $d$ copies of the same state. Finally, given a random choices of the QC, we identify the optimal linear combination of the phases that can be estimated with maximum sensitivity. Our scheme paves the ways for a variety of applications in distributed quantum sensing with photonic and atomic interferometers.We study an entangled distributed quantum sensing scheme based on an array of $d$ Mach-Zehnder interferometers (MZIs) for the estimation of relative phase shifts. The scheme uses $d$ coherent states and a single squeezed-vacuum state that is distributed among the MZIs by a quantum circuit (QC). The protocol can be optimized analytically: it overcomes the shot-noise limit and reaches the Heisenberg limit with respect to the average total number of probe particles, ${\overline{n}}_{T}$, for the estimation of arbitrary linear combinations of the $d$ phases. We compare the entangled strategy with a separable one that uses $d$ coherent and $d$ squeezed-vacuum states and the same ${\overline{n}}_{T}$. The entangled strategy benefits for a substantial reduction of resource overhead and can achieve a maximum gain equal to $d$ when using the same total squeezed-light intensity as the separable strategy. Interestingly, the entangled strategy using a single squeezed-vacuum state can reach the same sensitivity as the separable strategy that uses $d$ copies of the same state. Finally, given a random choices of the QC, we identify the optimal linear combination of the phases that can be estimated with maximum sensitivity. Our scheme paves the ways for a variety of applications in distributed quantum sensing with photonic and atomic interferometers.

Physical Review ASep 29, 202323 citations

Squeezed states in phase-sensing interferometers

Roy S. Bondurant, Jeffrey H. Shapiro

The performance of phase-sensing interferometers employing squeezed states and homodyne detection is analyzed and compared to the performance of systems employing direct detection. Standard differenced direct-detection Michelson and Mach-Zehnder interferometers are shown to be suboptimal in the sense that an observation/measurement-noise coupling occurs, which can degrade performance. Homodyne-detection interferometers in which the phase shift in one arm is the conjugate of that in the other arm do not suffer from the preceding drawback. Overall, however, the performance of differenced direct-detection and homodyne-detection interferometers is similar in single-frequency operation. In particular, both detection schemes reach the standard quantum limit on position-measurement sensitivity in single-frequency interferometric gravity-wave detectors at roughly the same average photon number. This limit arises from back action in the form of radiation pressure fluctuations entering through the energy-phase uncertainty principle. Multifrequency devices can circumvent this uncertainty principle, as illustrated by the conceptual design given for a two-frequency interferometer which can greatly surpass the standard quantum limit on position sensing. This configuration assumes that ideal photodetectors respond to photon flux rather than energy flux.The performance of phase-sensing interferometers employing squeezed states and homodyne detection is analyzed and compared to the performance of systems employing direct detection. Standard differenced direct-detection Michelson and Mach-Zehnder interferometers are shown to be suboptimal in the sense that an observation/measurement-noise coupling occurs, which can degrade performance. Homodyne-detection interferometers in which the phase shift in one arm is the conjugate of that in the other arm do not suffer from the preceding drawback. Overall, however, the performance of differenced direct-detection and homodyne-detection interferometers is similar in single-frequency operation. In particular, both detection schemes reach the standard quantum limit on position-measurement sensitivity in single-frequency interferometric gravity-wave detectors at roughly the same average photon number. This limit arises from back action in the form of radiation pressure fluctuations entering through the energy-phase uncertainty principle. Multifrequency devices can circumvent this uncertainty principle, as illustrated by the conceptual design given for a two-frequency interferometer which can greatly surpass the standard quantum limit on position sensing. This configuration assumes that ideal photodetectors respond to photon flux rather than energy flux.

Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fieldsDec 15, 1984299 citations

Measurement of the quantum states of squeezed light

Gerd Breitenbach, Stephan Schiller, J. Mlynek

NatureMay 1, 1997545 citations

We study an entangled distributed quantum sensing scheme based on an array of

d

Mach-Zehnder interferometers (MZIs) for the estimation of relative phase shifts. The scheme uses

d

coherent states and a single squeezed-vacuum state that is distributed among the MZIs by a quantum circuit (QC). The protocol can be optimized analytically: it overcomes the shot-noise limit and reaches the Heisenberg limit with respect to the average total number of probe particles,

{\overline{n}}_{T}

, for the estimation of arbitrary linear combinations of the

d

phases. We compare the entangled strategy with a separable one that uses

d

coherent and

d

squeezed-vacuum states and the same

{\overline{n}}_{T}

. The entangled strategy benefits for a substantial reduction of resource overhead and can achieve a maximum gain equal to

d

when using the same total squeezed-light intensity as the separable strategy. Interestingly, the entangled strategy using a single squeezed-vacuum state can reach the same sensitivity as the separable strategy that uses

d

copies of the same state. Finally, given a random choices of the QC, we identify the optimal linear combination of the phases that can be estimated with maximum sensitivity. Our scheme paves the ways for a variety of applications in distributed quantum sensing with photonic and atomic interferometers.