Quantum Reservoir Engineering with Laser Cooled Trapped Ions

We discuss the generation of entanglement between electronic states of two atoms in a cavity using direct quantum feedback schemes. We compare the effects of different control Hamiltonians and detection processes in the performance of entanglement production and show that the quantumjump-based feedback proposed by us in Phys. Rev. A 76 010301(R) (2007) can protect highly entangled states against decoherence. We provide analytical results that explain the robustness of jump feedback, and also analyse the perspectives of experimental implementation by scrutinising the effects of imperfections and approximations in our model.

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“…In this way, one can engineer the reservoir dynamics [29,30] via the transformation U to generate highly entangled states.…”

Section: The Modelmentioning

confidence: 99%

Controlling entanglement by direct quantum feedback

2008

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“…Although in recent years, superconducting circuit devices which allow in situ access to the amplitude of the qubit-resonator coupling have been realized [9][10][11][12], a scheme for controlling the phase of this coupling has only recently been demonstrated in [13]. Such a scheme is expected to be useful in a variety of settings, such as quantum gate operations [14], creating shaped photons for quantum networks [13,15,16], measuring the vacuum state of a cavity [17], exploring vacuum-induced Berry phases [18], enabling the controlled coupling of a single or multiple qubits to multiple resonator modes [19][20][21], or engineering quantum reservoirs [22].…”

Section: Introductionmentioning

confidence: 99%

Microwave-induced amplitude- and phase-tunable qubit-resonator coupling in circuit quantum electrodynamics

et al. 2015

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In the circuit quantum electrodynamics architecture, both the resonance frequency and the coupling of superconducting qubits to microwave field modes can be controlled via external electric and magnetic fields to explore qubit -photon dynamics in a wide parameter range. Here, we experimentally demonstrate and analyze a scheme for tuning the coupling between a transmon qubit and a microwave resonator using a single coherent drive tone. We treat the transmon as a three-level system with the qubit subspace defined by the ground and the second excited states. If the drive frequency matches the difference between the resonator and the qubit frequency, a Jaynes-Cummings type interaction is induced, which is tunable both in amplitude and phase. We show that coupling strengths of about 10 MHz can be achieved in our setup, limited only by the anharmonicity of the transmon qubit. This scheme has been successfully used to generate microwave photons with controlled temporal shape [Pechal et al., Phys. Rev. X 4, 041010 (2014)] and can be directly implemented with superconducting quantum devices featuring larger anharmonicity for higher coupling strengths.

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“…However, one can also use engineered dissipation to drive the system towards a desired non-trivial steady-state. (3) Both these aspects of dissipation are important in the system presented in this article.…”

Section: Introductionmentioning

confidence: 99%

Effects of quasiparticle tunnelling in a circuit-QED realization of a strongly driven two-level system

Leppäkangas

Graaf

Adamyan

et al. 2013

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. We experimentally and theoretically study the frequency shift of a driven cavity coupled to a superconducting charge qubit. In addition to previous studies, we here also consider drive strengths large enough to energetically allow for quasiparticle creation. Quasiparticle tunneling leads to the inclusion of more than two charge states in the dynamics. To explain the observed effects, we develop a master equation for the microwave dressed charge states, including quasiparticle tunneling. A bimodal behavior of the frequency shift as a function of gate voltage can be used for sensitive charge detection. However, at weak drives the charge sensitivity is significantly reduced by non-equilibrium quasiparticles, which induce transitions to a non-sensitive state. Unexpectedly, at high enough drives, quasiparticle tunneling enables a very fast relaxation channel to the sensitive state. In this regime, the charge sensitivity is thus robust against externally injected quasiparticles and the desired dynamics prevail over a broad range of temperatures. We find very good agreement between theory and experiment over a wide range of drive strengths and temperatures.

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Quantum Reservoir Engineering with Laser Cooled Trapped Ions

Cited by 712 publications

References 24 publications

Controlling entanglement by direct quantum feedback

Controlling entanglement by direct quantum feedback

Microwave-induced amplitude- and phase-tunable qubit-resonator coupling in circuit quantum electrodynamics

Effects of quasiparticle tunnelling in a circuit-QED realization of a strongly driven two-level system

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