Effect of bath temperature on the quantum decoherence

Abstract

The dynamics of a qubit in two different environments are investigated theoretically. The first environment is a two level system coupled to a bosonic bath. And the second one is a damped harmonic oscillator. Based on a unitary transformation, we find that the decoherence of the qubit can be reduced with increasing temperature $T$ in the first case, which agree with the results in [Phys. Rev. Lett. 100, 120401], whereas, it can not be reduced with $T$ in the second case. In both cases, the qubit dynamics are changed substantially as the coupling increases or finite detuning appears.Comment: 10 pages, 5 figure

Effect of bath temperature on the decoherence of quantum dissipative systems

“…This model has been studied in several previous articles [11,33] and has no exact analytical expression of the reduced density matrix for qubits. References [11,33] showed that bath temperature can enhance the coherence of qubit A; however, their conclusions are based on a Born-Markov approximation or weak-coupling approximation. In this paper, we recheck this conclusion by making use of stochastic decoupling along with HEOM which is beyond the usual Born-Markov and weak-coupling approximations.…”

“…Comparing with previous literature [11,33], we reexamine the decoherence dynamics of the two-qubit spin-boson model by making use of the nonperturbative HEOM formalism. Our results demonstrate that the anomalous decoherence phenomenon (decoherence reduced by increasing bath temperature) is independent of the Born-Markov approximation.…”

“…By making use of the generalized Silbey-Harris or Lang-Firsov transformation [7][8][9][10][11], one can obtain the effective decoherence rate of qubit A under WeisskopfWigner approximation as follows [11] …”

“…However, it was pointed out in Refs. [11,33] that the bosonic bath temperature can enhance the coherence in a two-qubit spin-boson model, where a bare qubit interacts with the other qubit which is coupled to a thermal bosonic bath. Nevertheless, their conclusions are based on the BornMarkov or weak coupling approximations.…”

“…The spinboson model has attracted considerable attention in past decades because it provides a universal model for numerous physical and chemical processes. The reduced system dynamics of spin-boson model has been studied by various analytical and numerical methods, for example, the polaron [5,6] or generalized Silbey-Harris [7][8][9][10][11][12] transformation approach, the time-dependent numerical renormalization group method [13][14][15][16], the quasi adiabatic propagator path integral, [9,17,18] and hierarchical equations of motion (HEOM) [19][20][21][22][23][24][25][26]. Each method has its own regimes of validity depending on the systembath coupling strength, the bath temperature and the bath spectral density function.…”