arXiv subjects

Chuan-Zhe Yao

Publications and source records attributed to Chuan-Zhe Yao.

5 recordsLinked to original sources

arXiv2024

Two-mode Open Quantum Systems: Decoherence and Localized Bound State Dynamics

Dissipationless localized bound states of open quantum systems are significantly robust to decoherence and have potential applications in quantum technologies. In this work, the decoherence dynamics and dissipationless localized bound states of a two-mode open quantum system are investigated. The conditions for the emergence of dissipationless localized bound states are analytically solved, and the corresponding critical system-environment couplings under different values of the inter-mode coupling and the detuning are determined. The decoherence dynamics of the system under such conditions are analyzed and dissipationless coherence between the different localized bound states against decoherence is clearly shown. This may provide a new avenue to develop dissipationless quantum technology for quantum operations.

quant-ph↗

arXiv2024

The strong-coupling quantum thermodynamics of quantum Brownian motion based on the exact solution of its reduced density matrix

We derive the quantum thermodynamics of quantum Brownian motion from the exact solution of its reduced density matrix. We start from the total equilibrium thermal state between the Brownian particle and its reservoir, and solve analytically and exactly the reduced density matrix of the system by taking the partial trace over all the reservoir states. We find that the reduced Hamiltonian and the reduced partition function of the Brownian motion must be renormalized significantly, as shown in the general nonperturbative renormalization theory of quantum thermodynamics for open quantum systems we developed recently [Phys. Rev. Res. 4, 023141 (2022)]. The reduced Hamiltonian contains not only a frequency shift but also a squeezing pairing interaction, where a momentum-dependent potential is generated naturally from the strong coupling between the Brownian particle and the reservoir, after traced over all the reservoir states. The resulting exact reduced density matrix of the Brownian motion is given by a squeezing thermal state. Moreover, beyond the weak coupling limit, in order to obtain correctly the reduced partition function of the Brownian motion, one must take into account the non-negligible changes of the reservoir state induced by the system-reservoir coupling. Using the exact solutions of the reduced density matrix, the reduced Hamiltonian as well as the reduced partition function of the Brownian motion, we show that the controversial results obtained from the different definitions of internal energy and the issue of the negative heat capacity in the previous studies of strong-coupling quantum thermodynamics are resolved.

quant-ph↗

arXiv2023

Quantum transport theory of hybrid superconducting systems

We present a quantum transport theory for hybrid superconducting systems based on our exact master equation approach. The total transient transport current is decomposed into components that describe coherent transports through different paths of particle and hole channels. We show that the coherent transports are resultant interferences of numerous repeated tunneling processes and cannot be rendered as a simple normal transmission or Andreev reflection as usually described quantum transport involving superconductivity. As a practical application, we find that the coherent transport currents passing through a pair of well-separated Majorana zero modes vanish due to the totally destructive interference between the particle and hole channels.

cond-mat.mes-hall↗

arXiv2021

The differential conductance tunnel spectroscopy in an analytical solvable two-terminal Majorana device

In this paper, we investigate the non-Markovian quantum transport dynamics of a two-terminal Majorana device that is made of an asymmetric topological superconducting chain coupled to two leads. This asymmetric superconducting chain is analytically solvable and can be realized by a hybrid system of semiconductor nanowire coupled to superconductors or by 1D transverse-field Ising chains. In such asymmetric superconducting chains, by the change of chemical potential, its ground state undergoes a topological quantum phase transition from the topological Majorana bound state to the trivial Andreev bound state while the ground state energy remains zero. We solve the exact transient transport current and the corresponding differential conductance. The results show that the presence or absence of the interference between the left and right Majorana zero modes plays an important role on the topological phase transition of conductance. It cause the edge-localized topologically trivial states to be insulated with zero conductance, while the nonlocally distributed topologically nontrivial states always have a quantized conductance 2e^2/h. This dramatic change associated with topological phase transition for zero-mode differential conductance at zero bias is independent of the structure of leads and the coupling strength. We also examine the finite size effect of the superconducting chain and the coherence effect between zero mode and non-zero energy modes on the differential conductance in this two-terminal Majorana device.

cond-mat.str-el↗

arXiv2020

Probing topological states through the exact non-Markovian decoherence dynamics of a spin coupled to a spin bath in real-time domain

In this paper, we explore the decoherence dynamics of a probing spin coupled to a spin bath, where the spin bath is given by a controllable 1D transverse-field Ising chain. The 1D transverse-field Ising chain with free-ends boundary condition is equivalent to a modified Kitaev model with non-local Majorana bound states in its topological phase. We find that the probing spin non-Markovian decoherence dynamics can manifest the topological structure of the spin chain. By controlling the external magnetic field on the Ising chain, we find the close relationships between the quantum phase transitions, the topological edge states, and the non-Markovian dynamics in real-time domain. We also investigate the corresponding quantum entanglement dynamics in this topological system.

cond-mat.str-el↗