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-symmetric circuit QED

Quijandría, Fernando; Naether, Uta; Özdemir, Şahin Kaya; Nori, Franco; Zueco, David

doi:10.1103/physreva.97.053846

Cited by 108 publications

(88 citation statements)

References 61 publications

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“…Fast control of dissipation in a superconducting resonator V. A. Sevriuk, 1 K. Y. Tan, 1 E. Hyyppä, 1 M. Silveri, 1, 2 M. Partanen, 1 M. Jenei, 1 S. Masuda, 1 J. Goetz, 1 V. Vesterinen, 3 L. Grönberg, 3 We report on fast tunability of an electromagnetic environment coupled to a superconducting coplanar waveguide resonator. Namely, we utilize a recently-developed quantum-circuit refrigerator (QCR) to experimentally demonstrate a dynamic tunability in the total damping rate of the resonator up to almost two orders of magnitude.…”

mentioning

confidence: 99%

Fast control of dissipation in a superconducting resonator

Sevriuk

Tan

Hyyppä

et al. 2019

Applied Physics Letters

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We report on fast tunability of an electromagnetic environment coupled to a superconducting coplanar waveguide resonator. Namely, we utilize a recently-developed quantum-circuit refrigerator (QCR) to experimentally demonstrate a dynamic tunability in the total damping rate of the resonator up to almost two orders of magnitude. Based on the theory it corresponds to a change in the internal damping rate by nearly four orders of magnitude. The control of the QCR is fully electrical, with the shortest implemented operation times in the range of 10 ns. This experiment constitutes a fast active reset of a superconducting quantum circuit. In the future, a similar scheme can potentially be used to initialize superconducting quantum bits.Tunable dissipative environments for circuit quantum electrodynamics (cQED) are pursued intensively in experiments due to the unique opportunities to study non-Hermitian physics 1,2 , such as phase transitions related to parity-time symmetry 3 , decoherence and quantum noise 4 . Interesting effects can be observed in experiments on exceptional points 5-7 , which also gives possibilities to use such systems as models in nonlinear photonics, for example, for metamaterials 8 and for photonic crystals 9 .From the practical point of view, tunable environments are utilized to protect and process quantum information 10-12 and to implement qubit reset 13,14 . The latter application calls for fast tunability of the environment due to the aim to increase the rate of the operations on a quantum computer. Recent advances in the field of cQED for quantum information processing 14-17 render this topic highly interesting.There are different ways for resetting superconducting qubits. Firstly, one may tune the qubit frequency to reduce its life time 18 . The disadvantages of this method include the broad frequency band reserved by the qubit and the required fast frequency sweep which may lead to an increased amount of initialization error 19 . Conventionally, it is beneficial to maintain the qubits at the optimal parameter points during all operations. Secondly, it is possible to use microwave pulses to actively drive the qubit to the ground state 20-23 . Such methods are popular because no additional components or new control steps are needed. However, to achieve high fidelity one usually needs to increase the reset time to the microsecond range. Thirdly, one can engineer a tunable environment for the qubits 13,24-26 . This approach demand changes in the chip design, but may lead to high fidelity for a fast reset without compromises on the other properties.Here, we focus on a single-parameter-controlled tunable environment implemented by a quantum-circuit refrigerator (QCR) 5,27-31 . The refrigerator is based on photonassisted electron tunneling through two identical normalmetal-insulator-superconductor junctions (NIS). It has been used to cool down a photon mode of the resonator 27 , and to observe a Lamb shift in a cQED system 31 . Furthermore, QCR can be used as a cryogenic photon source 29 , which ma...

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mentioning

confidence: 99%

Fast control of dissipation in a superconducting resonator

Sevriuk

Tan

Hyyppä

et al. 2019

Applied Physics Letters

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“…(36) The principal squeezing variances, determined along Eqs. (20) and (21), are obtained for arbitrary incident coherent states as:…”

Section: Parametric Down-conversion As the Source Of Non-classicamentioning

confidence: 99%

“…These EP-induced effects include: enhancement of sensing [17,25,42], lossinduced photon [16,43,44] and phonon [45,46] lasing, nonreciprocal light transmission [15,44], unidirectional invisibility [47,48], chiral modes and directional lasing [49], lasing with enhanced-mode selectivity [50,51], asymmetric mode switching [52], group velocity control via optomechanically-induced transparency [53], and enhanced optomechanical cooling [54], among many other effects. Applications of EPs are not limited to standard photonics, but also have been proposed for, e.g., microwave photonics using superconducting quantum circuits [20], quantum plasmonics [55] (for a review see [56]), electronics [57,58], metamaterials [59], cavity optomechanics [45,54,60], and acoustics [61,62]. The EPs, which correspond to PT phase transitions, are useful to reveal and describe dynamical phase transitions in condensed-matter open quantum systems and to classify their topological phases [63][64][65][66][67][68][69][70] or topological energy transfers [71].…”

Section: Introductionmentioning

confidence: 99%

Nonclassical light at exceptional points of a quantum PT -symmetric two-mode system

et al. 2019

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A two-mode optical parity-time (PT ) symmetric system, with gain and damping, described by a quantum quadratic Hamiltonian with additional small Kerr-like nonlinear terms, is analyzed from the point of view of nonclassical-light generation. Two kinds of stationary states with different types of (in)stability are revealed. Properties of one of these are related to the presence of semiclassical exceptional points, i.e., exotic degeneracies of the non-Hermitian Hamiltonian describing the studied system without quantum jumps. The evolution of the logarithmic negativity, principal squeezing variances, and sub-shot-noise photon-number correlations, considered as entanglement and nonclassicality quantifiers, is analyzed in the approximation of linear-operator corrections to the classical solution. Suitable conditions for nonclassical-light generation are identified in the oscillatory regime, especially at and around exceptional points that considerably enhance the nonlinear interaction and, thus, the non-classicality of the generated light. The role of quantum fluctuations, inevitably accompanying attenuation and amplification in the evolution of quantum states, is elucidated. The evolution of the system is analyzed for different initial conditions.

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“…1(a), there is an input (output) field a in (a out ) with frequency ω acting on the input (output) port of the cavity a. With the relation a ( j) out = S ( j) 21 (ω)a in , we can define the transmission coefficient S ( j) 21 (ω) of the passive cavity (see Appendix B),…”

Section: Readout Of a Qubit Around The Epmentioning

confidence: 99%

“…is the self-energy resulting from cavity b. If the transmission spectra S (g) 21 (ω) and S (e) 21 (ω) have a clear difference, the qubit state can then be resolved by measuring the transmission spectrum S ( j) 21 (ω) of the passive cavity. In the absence of the auxiliary cavity (i.e., J 1 = 0), the states of the qubit weakly coupled to a passive cavity cannot be resolved when using the dispersive readout method [see Fig.…”

Section: Readout Of a Qubit Around The Epmentioning

confidence: 99%

Dispersive readout of a weakly coupled qubit via the parity-time-symmetric phase transition

2019

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For some cavity-quantum-electrodynamics systems, such as a single electron spin coupled to a passive cavity, it is challenging to reach the strong-coupling regime. In such a weak-coupling regime, the conventional dispersive readout technique cannot be used to resolve the quantum states of the spin. Here we propose an improved dispersive readout method to measure the quantum states of a weakly coupled qubit by harnessing either one or two auxiliary cavities linearly coupled to the passive cavity containing the qubit. With appropriate parameters in both cases, the system excluding the qubit can exhibit a parity-time-symmetric phase transition at the exceptional point (EP). Because the EP can amplify the perturbation induced by the qubit and the parity-time symmetry can narrow the linewidths of the peaks in the transmission spectrum of the passive cavity, we can measure the quantum states of the weakly coupled qubit via this transmission spectrum. Owing to the weak coupling between the qubit and the passive cavity, the backaction due to the measurement of the qubit can also be reduced in comparison with the conventional dispersive readout technique in the strong-coupling regime.

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PT -symmetric circuit QED

Cited by 108 publications

References 61 publications

Fast control of dissipation in a superconducting resonator

Fast control of dissipation in a superconducting resonator

Nonclassical light at exceptional points of a quantum PT -symmetric two-mode system

Dispersive readout of a weakly coupled qubit via the parity-time-symmetric phase transition

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