The deterioration of precision caused by quantum decoherence in dissipative environments is a longstanding problem in the development of distributed quantum metrology. Therefore, it is significant to effectively overcome the entanglement-distribution loss and channel noise of dissipative environments and improve the measurement-sensitivity. Here, we introduce noiseless linear amplifier (NLA) based on photon catalysis into distributed phase estimation to mitigate the loss and noise. Through utilizing a series of reduction and equivalence relations to simplify the problem of distributed phase estimation to a single-parameter estimation situation, our results show that Photon catalysis (PC)-NLAs can effectively mitigate the loss and noise of dissipative environments, and greatly improve the measurement-sensitivity. More interestingly, we find that adding thermal photons of environment has positive contributions on the measurement-sensitivity under certain circumstances. Our scheme should prove valuable for the global wide-area quantum sensor network.
The deterioration of precision caused by quantum decoherence in dissipative environments is a longstanding problem in the development of distributed quantum metrology. Therefore, it is significant to effectively overcome the entanglement-distribution loss and channel noise of dissipative environments and improve the measurement-sensitivity. Here, we introduce noiseless linear amplifier (NLA) based on photon catalysis into distributed phase estimation to mitigate the loss and noise. Through utilizing a series of reduction and equivalence relations to simplify the problem of distributed phase estimation to a single-parameter estimation situation, our results show that Photon catalysis (PC)-NLAs can effectively mitigate the loss and noise of dissipative environments, and greatly improve the measurement-sensitivity. More interestingly, we find that adding thermal photons of environment has positive contributions on the measurement-sensitivity under certain circumstances. Our scheme should prove valuable for the global wide-area quantum sensor network.
Quantum states are essential resource for quantum-enhanced applications. Loss incurred in the distribution channel, however, dissipates the high signal-to-noise ratio advantage enjoyed by the squeezed state. Here, we first demonstrate noise immunity enhancement by using phase-sensitive amplifier (PSA) with measurement-based noiseless linear amplifier (MB-NLA). We explore the signal transfer capability with the amplifier in a noisy channel. The MB-NLA enhanced PSA has obvious suppression effect on channel noises, especially it has improvement for the noise contaminated signal. Better performance can be achieved by flexibly adjusting amplifier parameters. With the amplifier, it is promising to overcome the entanglement-distribution loss and show its superiority in squeezing based quantum sensing.
In this work, we address the central problem about how to effectively find the available precision limit of unknown parameters. In the framework of the quantum Ziv-Zakai bound (QZZB), we employ noiseless linear amplification (NLA)techniques to an initial coherent state (CS) as the probe state, and focus on whether the phase estimation performance is improved significantly in noisy scenarios, involving the photon-loss and phase-diffusion cases. More importantly, we also obtain two kinds of Heisenberg error limits of the QZZB with the NLA-based CS in these noisy scenarios, making comparisons with both the Margolus-Levitin (ML) type bound and the Mandelstam-Tamm (MT) type bound. Our analytical results show that in cases of photon loss and phase diffusion, the phase estimation performance of the QZZB can be improved remarkably by increasing the NLA gain factor. Particularly, the improvement is more pronounced with severe photon losses. Furthermore in minimal photon losses, our Heisenberg error limit shows better compactness than the cases of the ML-type and MT-type bounds. Our findings will provide an useful guidance for accomplishing more complex quantum information processing tasks.
The entanglement structure between different frequency components within broadband quantum light pulses, forged at entanglement creation, represents a promising route to the practical delivery of many multipartite quantum information applications. However, the scalability of such applications is largely limited by the entanglement decoherence caused by photon loss. One promising method to combat such losses is noiseless linear amplification. However, while there have been various procedures that implement noiseless linear amplification on single-mode states, no realization has thus far been proposed for noiseless linear amplification on quantum states carrying a multimode structure. In this work we close this gap, proposing a noiseless linear amplifier (NLA) with photon catalysis (PC), namely, the PC-NLA. Constructing a multimode version of an existing NLA that uses quantum scissors (QS), the QS-NLA, we then show how the PC-NLA is compatible with the QS-NLA, even though the former uses half the physical resources of the latter. We then apply our multimode NLA frameworks to the problem of continuous-variable (CV) entanglement distillation, determining how the multimode structure of the entanglement impacts the performance of the NLAs. Different from single-mode NLA analyses, we find that a multimode NLA is only effective as a CV entanglement distillation strategy when the channel loss is beyond some threshold---a threshold largely dependent on the multimode structure. The results provided here will be valuable for real-world implementations of multipartite quantum information applications that utilize complex entanglement structure within broadband light pulses.
The deterioration of precision caused by quantum decoherence in dissipative environments is a longstanding problem in the development of quantum metrology. Therefore, it is significant to effectively analyze the evolution of quantum systems under dissipative environments and quantitatively estimate the parameters given a certain probe. Here, we propose a continuous-variable (CV) quantum metrology scheme within the Bayesian paradigm to estimate phase shift, loss coefficient and temperature of a dissipative environment. Through simulation analysis, we investigate the achievable precision of Bayesian quantum parameter estimation with Gaussian states and homodyne measurements, and the influence of different parameters on the estimation process. More interestingly, the scheme can be applied in more practical scenarios where not enough measurements are obtained and the frequentist analysis is not well defined.
Correlated interferometry offers various advantages in precision measurements, such as sub-shot noise sensitivity, high resolution, and prevention of detector saturation benefiting from dark output. In certain practical scenarios, e.g. absorptive measurement, there is usually unbalanced loss between the probe and reference beams, which destroys the correlation and remains a significant obstacle in the efficient application of entanglements. Here, we study the performance of a nonlinear interferometer whose arms experience unbalanced loss and demonstrate the use of a phase-sensitive amplifier in the sensing or reference arms to amplify or squeeze the light field, which can both reduce the degradation of quantum enhancement from unbalanced absorption in a lossy environment. We find that the loss after amplification, i.e. from imperfect interferometry and detection, can be mitigated when the phase-sensitive amplifier is placed at the sensing arm and functions as a noiseless amplifier. Our approach may be helpful to the practical application of quantum-enhanced absorptive measurement.
The research focused on enhancing the measurement accuracy through the use of non-Gaussian states has garnered increasing attention. In this study, we propose a scheme to input the coherent state mixed with a photon-catalyzed squeezed vacuum state into the Mach-Zender interferometer to enhance phase measurement accuracy. The findings demonstrate that photon catalysis, particularly multi-photon catalysis, can effectively improve the phase sensitivity of parity detection and the quantum Fisher information. Moreover, the situation of photon losses in practical measurement was studied. The results indicate that external dissipation has a greater influence on phase sensitivity than the internal dissipation. Compared to input coherent state mixed with squeezed vacuum state, the utilization of coherent state mixed photon-catalyzed squeezed vacuum state, particularly the mixed multi-photon catalyzed squeezed vacuum state as input, can enhance the phase sensitivity and quantum Fisher information. Furthermore, the phase measurement accuracy can exceed the standard quantum limit, and even surpass the Heisenberg limit. This research is expected to significantly contribute to quantum precision measurement.