The thermometry precision of a sample is a question of both fundamental and technological importance. In this paper, we consider a ring-structure system as our probe to estimate the temperature of a bath. Based on the Markovian master equation of the probe, we calculate the quantum Fisher information (QFI) of the probe at any time. We find that for the thermal equilibrium thermometry, the ferromagnetic structure can measure a lower temperature of the bath with a higher precision compared with the non-structure probe. While for the dynamical thermometry, the antiferromagnetic structure can make the QFI of the probe in the dynamical process much larger than that in equilibrium with the bath, which is somewhat counterintuitive. Moreover, the best accuracy for the thermometry achieved in the antiferromagnetic structure case can be much higher than that in the non-structure case. The physical mechanisms of above phenomena are given in this paper.

Although the radical pair (RP) model is widely accepted for birds' orientation, the physical mechanism of it is still not fully understood. In this paper we consider the RP model in the total angular-momentum representation and clearly show a detailed mechanism for orientation. When only the vertical hyperfine (HF) coupling component is considered, analytical expressions of singlet yield angular profiles are obtained with and without considering the radio frequency field, and when the horizontal HF coupling components are considered, a numerical calculation of the singlet yield is given. Based on these analytical and numerical results we present a detailed account of the following issues: how the HF coupling induces the singlet-triplet conversion; why the vertical radio frequency field can disorient the birds, while the parallel one cannot; and why the birds are able to "train" to different field strengths. Finally, we consider a multinuclei RP model.

We consider a model of an optical cavity with a nonequilibrium reservoir consisting of a beam of identical two-level atom pairs (TLAPs) in the general X state. We find that coherence of multiparticle nonequilibrium reservoir plays a central role on the potential work capability of the cavity. We show that no matter whether there are quantum correlations in each TLAP (including quantum entanglement and quantum discord) or not, the coherence of the TLAPs has an effect on the work capability of the cavity. Additionally, constructive and destructive interferences could be induced to influence the work capability of the cavity by adjusting only the relative phase, with which quantum correlations have nothing to do. In this paper, the coherence of the reservoir, rather than the quantum correlations, effectively reflecting the effects of the reservoir on the system's work capability is demonstrated clearly.

We propose a novel scheme of feed-forward control and its reversal for protecting quantum state against decoherence. Before the noise channel our pre-weak measurement and feed-forward are just to change the protected state into the state almost immune to the noise channel, and after the channel our reversed operations and post-weak measurements are just to restore the protected state. Unlike most previous state protection schemes, ours only concerns the noise channel and does not care about the protected state. We show that our scheme can effectively protect unknown states, nonorthogonal states and entangled states against amplitude damping noise. Our scheme has dramatic merits of protecting quantum states against heavy amplitude damping noise, and can perfectly protect some specific nonorthogonal states in an almost deterministic way, which might be found some applications in current quantum communication technology. And it is most important that our scheme is experimentally available with current technology

We investigate the heat transport between two nonthermal reservoirs based on a microscopic collision model. We consider a bipartite system consisting of two identical subsystems, and each subsystem interacts with its own local reservoir, which consists of a large collection of initially uncorrelated ancillas. Then a heat transport is formed between two reservoirs by a sequence of pairwise collisions (intersubsystem and subsystem-local reservoir). In this paper we consider two kinds of the reservoir's initial states: the thermal state and the state with coherence whose diagonal elements are the same as that of the thermal state and the off-diagonal elements are nonzero. In this way, we define the effective temperature of the reservoir with coherence according to its diagonal elements. We find that for two reservoirs having coherence the direction of the steady current of heat is different for different phase differences between the two initial states of two reservoirs, especially the heat can transfer from the "cold reservoir" to the "hot reservoir" in the steady regime for particular phase difference. In the limit of the effective temperature difference between the two reservoirs ΔT→0, for most of the phase differences, the steady heat current increases with the increase of effective temperature until it reaches the high effective temperature limit, while for the thermal state or particular phase difference the steady heat current decreases with the increase of temperature at high temperatures, and in this case the conductance can be obtained.