Gaussian quantum estimation of the loss parameter in a thermal environment

Abstract

Lossy bosonic channels play an important role in a number of quantum information tasks, since they well approximate thermal dissipation in an experiment. Here, we characterize their metrological power in the idler-free and entanglement-assisted cases, using respectively single- and two-mode Gaussian states as probes. In the problem of estimating the loss parameter, we study the power-constrained quantum Fisher information (QFI) for generic temperature and loss parameter regimes, showing qualitative behaviours of the optimal probes. We show semi-analytically that the two-mode squeezed-vacuum state optimizes the QFI for any value of the loss parameter and temperature. We discuss the optimization of the {\it total} QFI, where the number of probes is allowed to vary by keeping the total power constrained. In this context, we elucidate the role of the ``shadow-effect'', or passive signature, for reaching a quantum advantage. Finally, we discuss the implications of our results for the quantum illumination and quantum reading protocols.

Quantum loss sensing with two-mode squeezed vacuum state under noisy and lossy environment

“…By carefully choosing the quantum state of the probe beam as well as the measurement performed on the scattered light, one can enhance the SNR without increasing the intensity of the probe beam 8 . Among various types of parameter estimation problems treated in the framework of quantum sensing, the so-called loss sensing, understood to be conjugate to phase sensing, is directly related to optical spectroscopy in that it aims to precisely measure the amount of energy that is lost during propagation through an analyte [9][10][11][12][13][14][15] .…”

“…The TMSV state possesses strong quantum correlations between the two modes in photon number, frequency, time, and position. By exploiting such correlations, the TMSV state has proven to be extremely useful in many quantum technological applications 1, 18-23 including single [9][10][11][12][13][14] and multi-parameter loss sensing 15 . In particular, the recent experimental work demonstrated that a loss sensing scheme that uses the TMSV state along with coincidence detection is more robust to thermal noise compared with a classical scheme that uses the coherent state 1 .…”

Quantum loss sensing with two-mode squeezed vacuum state under noisy and lossy environment

“…The TMSV state possesses strong quantum correlations between the two modes in photon number, frequency, time, and position. By exploiting such correlations, the TMSV state has proven to be extremely useful in many quantum technological applications 1 , 18 – 23 including single 9 – 14 and multi-parameter loss sensing 15 . In particular, the recent experimental work demonstrated that a loss sensing scheme that uses the TMSV state along with coincidence detection is more robust to thermal noise compared with a classical scheme that uses the coherent state 1 .…”

“…By carefully choosing the quantum state of the probe beam as well as the measurement performed on the scattered light, one can enhance the SNR without increasing the intensity of the probe beam 8 . Among various types of parameter estimation problems treated in the framework of quantum sensing, the so-called loss sensing, understood to be conjugate to phase sensing, is directly related to optical spectroscopy in that it aims to precisely measure the amount of energy that is lost during propagation through an analyte [9][10][11][12][13][14][15] .One of the most practical states used in quantum sensing is the two-mode squeezed vacuum (TMSV) state, which can be generated via spontaneous parametric down-conversion in a nonlinear crystal 16,17 . The TMSV state possesses strong quantum correlations between the two modes in photon number, frequency, time, and position.…”

Quantum-enhanced Doppler lidar

“…Of particular interest for remote sensing applications is the QI protocol, where the aim is to detect the presence of a weakly reflecting target with an error probability smaller than using the best classical strategy. Here, a quantum advantage in the error probability exponent can be achieved by using a global measurement (up to 6 dB) [24][25][26][27][28] , or by using local measurements (up to 3 dB) [29][30][31] . This advantage is only achieved in a very noisy environment, such as the case of room-temperature microwave band, by a large bandwidth two-mode squeezed-vacuum state 3 .…”