Dian Utami - Academia.edu (original) (raw)
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Papers by Dian Utami
Physical Review A, 2007
We demonstrate theoretically how photon number statistics of a driven, damped oscillator at finit... more We demonstrate theoretically how photon number statistics of a driven, damped oscillator at finite temperature can be extracted by measuring the dephasing spectrum of a two-level system dispersively coupled to the oscillator; we thus extend the work of Dykman (1987) and Gambetta et al. (2006). We carefully consider the fidelity of this scheme-- to what extent does the measurement reflect the initial number statistics of the mode? We also derive analytic results for the dephasing of a qubit by a driven, thermal mode, and compare results obtained at different levels of approximation. Our results have relevance both to experiments in circuit cavity QED, as well as to nano-electromechanical systems.
Over the recent years, finding signatures of entanglement in macroscopic systems has been a centr... more Over the recent years, finding signatures of entanglement in macroscopic systems has been a central goal in many aspects of mesoscopic physics. Here we present our study of non-equilibrium entanglement dynamics between a qubit and a nanomechanical resonator that is coupled to a phonon bath. Unlike previous studies, we specifically look at dispersively coupled qubit-oscillator system which has been realized in many different experiments. Using master equation expressed in gaussian wigner functions, we obtained an elegant and intuitive expression for the entanglement. Two ways of generating entanglement were found; entanglement of the qubit to the amplitude of the driven oscillator and to the phase of the oscillator. A full analytical result within the zero temperature limit of the two cases were derived. We also investigate the effect of finite temperature to the entanglement dynamics and found the phase entanglement to be more robust against temperature. The result indicates that an indirect method to measure the presence of entanglement in the system is possible.
Physical Review A, 2008
We study entanglement dynamics in a system consisting of a qubit dispersively coupled to a finite... more We study entanglement dynamics in a system consisting of a qubit dispersively coupled to a finite-temperature, dissipative, driven oscillator. We show that there are two generic ways to generate entanglement: one can entangle the qubit either with the phase or the amplitude of the oscillator's motion. Using an exact solution of the relevant quantum master equation, we study the robustness of both these kinds of entanglement against the effects of dissipation and temperature; in the limit of zero temperature (but finite damping), a simple analytic expression is derived for the logarithmic negativity. We also discuss how the generated entanglement may be detected via dephasing revivals, being mindful that revivals can occur even in the absence of any useful entanglement. Our results have relevance to quantum electromechanics, as well as to circuit QED systems.
Physical Review A, 2007
We demonstrate theoretically how photon number statistics of a driven, damped oscillator at finit... more We demonstrate theoretically how photon number statistics of a driven, damped oscillator at finite temperature can be extracted by measuring the dephasing spectrum of a two-level system dispersively coupled to the oscillator; we thus extend the work of Dykman (1987) and Gambetta et al. (2006). We carefully consider the fidelity of this scheme-- to what extent does the measurement reflect the initial number statistics of the mode? We also derive analytic results for the dephasing of a qubit by a driven, thermal mode, and compare results obtained at different levels of approximation. Our results have relevance both to experiments in circuit cavity QED, as well as to nano-electromechanical systems.
Over the recent years, finding signatures of entanglement in macroscopic systems has been a centr... more Over the recent years, finding signatures of entanglement in macroscopic systems has been a central goal in many aspects of mesoscopic physics. Here we present our study of non-equilibrium entanglement dynamics between a qubit and a nanomechanical resonator that is coupled to a phonon bath. Unlike previous studies, we specifically look at dispersively coupled qubit-oscillator system which has been realized in many different experiments. Using master equation expressed in gaussian wigner functions, we obtained an elegant and intuitive expression for the entanglement. Two ways of generating entanglement were found; entanglement of the qubit to the amplitude of the driven oscillator and to the phase of the oscillator. A full analytical result within the zero temperature limit of the two cases were derived. We also investigate the effect of finite temperature to the entanglement dynamics and found the phase entanglement to be more robust against temperature. The result indicates that an indirect method to measure the presence of entanglement in the system is possible.
Physical Review A, 2008
We study entanglement dynamics in a system consisting of a qubit dispersively coupled to a finite... more We study entanglement dynamics in a system consisting of a qubit dispersively coupled to a finite-temperature, dissipative, driven oscillator. We show that there are two generic ways to generate entanglement: one can entangle the qubit either with the phase or the amplitude of the oscillator's motion. Using an exact solution of the relevant quantum master equation, we study the robustness of both these kinds of entanglement against the effects of dissipation and temperature; in the limit of zero temperature (but finite damping), a simple analytic expression is derived for the logarithmic negativity. We also discuss how the generated entanglement may be detected via dephasing revivals, being mindful that revivals can occur even in the absence of any useful entanglement. Our results have relevance to quantum electromechanics, as well as to circuit QED systems.