Discriminating quantum field theories in non-inertial frames

Abstract

Quantum channel discrimination is used to test quantum field theory in non-inertial frames. We search for optimal strategies which can best see the thermality of the Unruh effect. We find that the usual strategy of counting particles in the vacuum can be improved, thereby enhancing the discrimination. Coherent state probes, which are practical and feasible, give exponential improvement in the discrimination of the Unruh channel and come very close to optimal. In particular, we show that using a short pulse laser, the accelerations required to test the Unruh effect can be reduced by at least three orders of magnitude with the same statistical confidence as could be achieved in vacuum. These results are expected to be relevant to upcoming experimental tests of quantum field theory in curved spacetimes in analogue systems.

Ultimate Precision of Adaptive Noise Estimation

“…Here we find that the ultimate error probability for discriminating two teleportation-covariant channels is reached without adaptiveness and determined by their Choi matrices. Applications are for protocols of quantum sensing, such as quantum reading [35][36][37][38][39][40][41][42] and illumination [43][44][45][46], and for the resolution of extremely-close temperatures [47,48].Adaptive protocols for quantum parameter estimation.-The most general adaptive protocol for quantum parameter estimation can be formulated as follows. Let us consider a box containing a quantum channel E θ characterized by an unknown classical parameter θ.…”

“…For the specific case ofn T = 0 (infinitesimal discrimination from vacuum noise), we have a discontinuity and we may write Σ = dn T [60]. These results represent the ultimate adaptive limits for resolving two temperatures, e.g., for testing the Unruh effect [47] or the Hawking radiation in analogue systems [48].Conclusions.-In this paper we have established the ultimate limits of adaptive noise estimation and discrimination for the wide class of teleportation-covariant channels, which includes fundamental transformations for qubits, qudits and bosonic systems. We have reduced the most general adaptive protocols for parameter estimation and channel discrimination into much simpler block versions, where the output states are simply expressed in terms of Choi matrices of the encoding channels.…”

“…Here we find that the ultimate error probability for discriminating two teleportation-covariant channels is reached without adaptiveness and determined by their Choi matrices. Applications are for protocols of quantum sensing, such as quantum reading [35][36][37][38][39][40][41][42] and illumination [43][44][45][46], and for the resolution of extremely-close temperatures [47,48].…”

Entanglement enhanced thermometry in the detection of the Unruh effect

“…In order to detect the Unruh effect several metrological tools have been employed. Different approaches include using Gaussian probes [56], applying the framework of open quantum systems to compute Fisher information and quantum Fisher information [57], and using the technique of quantum channel discrimination [58].…”

Gravitational parameter estimation in a waveguide

“…Earlier work showed that the mode entanglement generated by the expansion of the universe encodes the expansion rate of the universe [16]. Also is was shown that phase estimation techniques could be employed to measure the Unruh effect at accelerations that are within experimental reach [11] (see also [17] for the application of channel discrimination to such experiments).…”