Abstract:The initial entanglement shared between inertial and accelerated observers degrades due to the influence of the Unruh effect. Here, we show that the Unruh effect can be completely eliminated by the technique of partial measurement. The lost entanglement could be entirely retrieved or even amplified, which is dependent on whether the optimal strength of reversed measurement is stateindependent or state-dependent. Our work provides a novel and unexpected method to recover the lost entanglement under Unruh decohe… Show more
“…In addition, when this common measurement strength increases FoutPMfalse(φfalse) is protected much better for π2≤ϑ<π; it even increases surprisingly with an increase in acceleration for π2<ϑ<π, in the limit p → 1 and q → 1. In addition, our numerical calculation shows that, in order to protect the QFI with respect to φ and QRs of the teleported state against the Unruh effect, we can use the following special choice for PMR strength [67]: qs=1−false(1−pfalse)cos2r. In fact, the Unruh noise may be approximately eliminated provided that the PM strength is sufficiently strong ( p → 1) and the above choice for the PMR is applied (see dashed lines in figure 8). Figure 8QFI of the single-qubit teleported state with respect to the phase parameter, φ, as a function of the acceleration parameter r by fixing θ=π2 for ( a ) 0<ϑ<π2, ( b ) ϑ=π2 and ( c ) π2<ϑ<π.…”
Section: Single-qubit Teleportation Under the Unruh Noise Channelmentioning
We address the teleportation of single- and two-qubit quantum states, parametrized by weight
θ
and phase
ϕ
parameters, in the presence of the Unruh effect experienced by a mode of a free Dirac field. We investigate the effects of the partial measurement (PM) and partial measurement reversal (PMR) on the quantum resources and quantum Fisher information (QFI) of the teleported states. In particular, we discuss the optimal behaviour of the QFI, quantum coherence (QC) as well as fidelity with respect to the PM and PMR strength and examine the effect of the Unruh noise on optimal estimation. It is found that, in the single-qubit scenario, the PM (PMR) strength at which the optimal estimation of the phase parameter occurs is the same as the PM (PMR) strength with which the teleportation fidelity and the QC of the teleported single-qubit state reaches its maximum value. On the other hand, generalizing the results to two-qubit teleportation, we find that the encoded information in the weight parameter is better protected against the Unruh noise in two-qubit teleportation than in the one-qubit scenario. However, extraction of information encoded in the phase parameter is more efficient in single-qubit teleportation than in the two-qubit version.
“…In addition, when this common measurement strength increases FoutPMfalse(φfalse) is protected much better for π2≤ϑ<π; it even increases surprisingly with an increase in acceleration for π2<ϑ<π, in the limit p → 1 and q → 1. In addition, our numerical calculation shows that, in order to protect the QFI with respect to φ and QRs of the teleported state against the Unruh effect, we can use the following special choice for PMR strength [67]: qs=1−false(1−pfalse)cos2r. In fact, the Unruh noise may be approximately eliminated provided that the PM strength is sufficiently strong ( p → 1) and the above choice for the PMR is applied (see dashed lines in figure 8). Figure 8QFI of the single-qubit teleported state with respect to the phase parameter, φ, as a function of the acceleration parameter r by fixing θ=π2 for ( a ) 0<ϑ<π2, ( b ) ϑ=π2 and ( c ) π2<ϑ<π.…”
Section: Single-qubit Teleportation Under the Unruh Noise Channelmentioning
We address the teleportation of single- and two-qubit quantum states, parametrized by weight
θ
and phase
ϕ
parameters, in the presence of the Unruh effect experienced by a mode of a free Dirac field. We investigate the effects of the partial measurement (PM) and partial measurement reversal (PMR) on the quantum resources and quantum Fisher information (QFI) of the teleported states. In particular, we discuss the optimal behaviour of the QFI, quantum coherence (QC) as well as fidelity with respect to the PM and PMR strength and examine the effect of the Unruh noise on optimal estimation. It is found that, in the single-qubit scenario, the PM (PMR) strength at which the optimal estimation of the phase parameter occurs is the same as the PM (PMR) strength with which the teleportation fidelity and the QC of the teleported single-qubit state reaches its maximum value. On the other hand, generalizing the results to two-qubit teleportation, we find that the encoded information in the weight parameter is better protected against the Unruh noise in two-qubit teleportation than in the one-qubit scenario. However, extraction of information encoded in the phase parameter is more efficient in single-qubit teleportation than in the two-qubit version.
“…Weak measurements only barely disturb the system by state collapse, thereby retaining the measured state reversible [44][45][46][47]. The elements of our pre-weak measurement could be formally written as [48]…”
Section: B Pre-and Post-weak Measurementsmentioning
It is commonly believed that the fidelity of quantum teleportation in the gravitational field would be degraded due to the heat up by the Hawking radiation. In this paper, we point out that the Hawking effect could be eliminated by the combined action of pre-and post-weak measurements, and thus the teleportation fidelity is almost completely protected. It is intriguing to notice that the enhancement of fidelity could not be attributed to the improvement of entanglement, but rather to the probabilistic nature of weak measurements. Our work extends the ability of weak measurements as a quantum technique to battle against gravitational decoherence in relativistic quantum information.
“…[10][11][12][13][14] Various approaches for protecting parameter precision against noise have been proposed, such as quantum error correction, [15][16][17] dynamical decoupling, [18] optimal feedback control, [19] correlated effects of the noisy channels, [20,21] and non-Markovianity of the environments. [22][23][24] In addition to the strategies mentioned above, weak measurement (WM) [25][26][27][28][29][30][31][32][33][34][35][36] and environment-assisted measurement (EAM) [37][38][39][40][41] are receiving increasing attentions as new techniques to combat the dissipative noise. A WM operation is an extension of the traditional von Neumann projective measurement.…”
Since the initial discovery of quantum teleportation, it is devoted to transferring unknown quantum states from one party to another distant partner. However, in the scenarios of remote sensing, what people truly care about is the information carried by certain parameters. The problem of multiparameter estimation in the framework of qutrit teleportation under amplitude damping (AD) noise is studied. Particularly, two schemes are proposed to battle against AD noise and enhance the precision of multiparameter estimation by utilizing weak measurement (WM) and environmentassisted measurement (EAM). For two-phase parameters encoded in a qutrit state, the analytical formulas of the quantum Fisher information matrix (QFIM) can be obtained. The results prove that the scheme of EAM outperforms the WM one in the improvements of both independent and simultaneous estimation precision. Remarkably, the EAM scheme can completely ensure the estimation precision against the contamination by AD noise. The reason should be attributed to the fact that EAM is carried out after the AD noise. Thus, it extracts information from both the system and the environment. The findings show that the techniques of WM and EAM are helpful for remote quantum sensing and can be generalized to other qutrit-based quantum information tasks under AD decoherence.
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