Cavity quantum electrodynamics using a near-resonance two-level system: Emergence of the Glauber state

Sarabi, Bahman; Ramanayaka, Aruna; Burin, Alexander L.; Wellstood, F. C.; Osborn, Kevin

doi:10.1063/1.4918775

Cited by 20 publications

(22 citation statements)

References 31 publications

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“…Experiments to realize the breakdown of photon blockade in zero dimensions are feasible, on the other hand. Indeed, adding to the one previous experiment with strong coherent drive [67], very recently, a coherent quantum-to-Glauber-state transition for a two-level system coupled to a microwave resonator has been experimentally observed [72].…”

Section: Discussionmentioning

confidence: 99%

Breakdown of Photon Blockade: A Dissipative Quantum Phase Transition in Zero Dimensions

2015

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The Jaynes-Cummings model with coherent drive is considered as an example of a nonlinear oscillator exhibiting photon blockade, where blockade by one, two, three, etc., photons occurs at a sequence of multiphoton absorption resonances. It is shown that with increasing drive strength, the blockade breaks down by way of a dissipative quantum phase transition. The transition is first order, except at a critical point in the space of drive amplitude and detuning, where a continuous transition is observed. Numerical solutions to the quantum master equation in the steady state are presented and compared with mean-field treatments based on Jaynes and Cummings' semiclassical equations (strong coupling with conserved pseudospin) and the Maxwell-Bloch equations (spontaneous emission included). The concept of a "thermodynamic limit" in the absence of conserved particle number is explored. Contrasting the identity of large photon number with weak coupling (large volume) in other dissipative quantum phase transitions for photons (e.g., in the phase-transition analogy of laser threshold), the limit of large photon numbers is a strong-coupling limit.

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Section: Discussionmentioning

confidence: 99%

Breakdown of Photon Blockade: A Dissipative Quantum Phase Transition in Zero Dimensions

2015

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“…While significant deviations from Eq. (2) have been observed 25,26 , these have been understood to arise from TLS interactions 27,28 or a distribution of TLS dipole moments 29 .…”

Section: Loss From Two-level Systemsmentioning

confidence: 99%

Effects of nonequilibrium quasiparticles in a thin-film superconducting microwave resonator under optical illumination

et al. 2016

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We have illuminated a thin-film superconducting Al lumped-element microwave resonator with 780 nm light and observed the resonator quality factor and resonance frequency as a function of illumination and microwave power in the 20 to 300 mK temperature range. The optically-induced microwave loss increases with increasing illumination but decreases with increasing microwave power. Although this behavior may suggest the presence of optically activated two-level systems, we find that the loss is better explained by the presence of nonequilibrium quasiparticles generated by the illumination and excited by the microwave drive. We model the system by assuming that the illumination creates an effective source of phonons with energy higher than double the superconducting gap and solve the coupled quasiparticle-phonon rate equations. We fit the simulation results to our measurements and find good agreement with the observed dependence of the resonator quality factor and frequency shift on temperature, microwave power, and optical illumination. Examination of the model reveals approaches to reducing optically-induced loss and improving the relaxation time of superconducting quantum devices.

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“…This tuning distinguishes it from an earlier study of the vacuum Rabi splitting and Glauber state made with a TLS [22]. TLSs are chosen for analysis only near an observed energy minima, which reveals the tunneling energies ∆ 0 .…”

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Projected Dipole Moments of Individual Two-Level Defects Extracted Using Circuit Quantum Electrodynamics

et al. 2016

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Material-based two-level systems (TLSs), appearing as defects in low-temperature devices including superconducting qubits and photon detectors, are difficult to characterize. In this study we apply a uniform dc-electric field across a film to tune the energies of TLSs within. The film is embedded in a superconducting resonator such that it forms a circuit quantum electrodynamical (cQED) system. The energy of individual TLSs is observed as a function of the known tuning field. By studying TLSs for which we can determine the tunneling energy, the actual pz, dipole moments projected along the uniform field direction, are individually obtained. A distribution is created with 60 pz. We describe the distribution using a model with two dipole moment magnitudes, and a fit yields the corresponding values p = p1 = 2.8 ± 0.2 Debye and p = p2 = 8.3 ± 0.4 Debye. For a strong-coupled TLS the vacuum-Rabi splitting can be obtained with pz and tunneling energy. This allows a measurement of the circuit's zero-point electric field fluctuations, in a method that does not need the electric-field volume.PACS numbers: 03.67.-a, 03.67. Pp, 33.15.Kr, 66.35.+a Dielectric two-level systems (TLSs) have attracted the attention of the quantum computing community ever since they were identified as a major source of decoherence in superconducting qubits [1]. Subsequent studies found that TLSs were also a performance-limiting source of noise in photon detectors used for astronomy [2,3]. This motivation has led to quantum characterization of TLSs in the tunneling barrier of superconducting qubits [1,4] and both noise and loss characterization in high quality superconducting resonator circuits. Thus TLSs are found as defects in various dielectric structures: deposited insulating films [1,5,6], Josephson Junction (JJ) tunneling barriers [1,7,8], imperfect interfaces between superconducting films with crystalline substrates [9], and the native oxides on materials [10]. Recent modeling has predicted possible structures and values for the TLS dipole moment [11][12][13]. While these TLSs are generally known to be charged atomic configurations that spatially tunnel, their microscopic structure and elemental composition are generally unknown.In a qubit made from an anharmonic oscillator the interaction energy is observed as a spectroscopic splitting in the qubit state. However, this quantity is not only dependent on circuit element parameters, but also on the thickness of the tunneling barrier [1]. The barrier has a thickness variation of 1-2 nm [14], such that this lack of accuracy is also present in the electric field amplitude and the measured TLS dipole moment. In general, individual measurements of TLSs within JJs find the transition dipole moment p tr = p z ∆ 0 /E, where p z ≡ |p z | is the absolute value of the dipole moment projected in the field direction, and the TLS tunneling energy over the total energy ∆ 0 /E is generally unknown. As a result only a lower bound of p z is determined from those measurements (∆ 0 /E ≤ 1). However, in studie...

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Cavity quantum electrodynamics using a near-resonance two-level system: Emergence of the Glauber state

Cited by 20 publications

References 31 publications

Breakdown of Photon Blockade: A Dissipative Quantum Phase Transition in Zero Dimensions

Breakdown of Photon Blockade: A Dissipative Quantum Phase Transition in Zero Dimensions

Effects of nonequilibrium quasiparticles in a thin-film superconducting microwave resonator under optical illumination

Projected Dipole Moments of Individual Two-Level Defects Extracted Using Circuit Quantum Electrodynamics

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