Continuous measurement of a qudit using dispersively coupled radiation

Steinmetz, John; Das, Debmalya; Siddiqi, Irfan; Jordan, Andrew N.

doi:10.1103/physreva.105.052229

Cited by 8 publications

(2 citation statements)

References 82 publications

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“…( 13) and ( 14) can be used to perform (continuous) quantum measurements on a qudit via measuring the photo-current of a nearby superconducting (SC) resonator [12,13] (see also recent paper, Ref. [27]). The simplest example could be a DQD singlet-triplet qubit, which has three relevant levels and the qubit subspace has no dipole moment for any DQD detunning (see Sec.…”

Section: N-level Effective Hamiltonians In Thementioning

confidence: 99%

Modulated longitudinal gates on encoded spin qubits via curvature couplings to a superconducting cavity

Ruskov

Tahan

2021

Phys. Rev. B

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Understanding how and to what magnitude solid-state qubits couple to metallic wires is crucial to the design of quantum systems such as quantum computers. Here, we investigate the coupling between a multi-level system, or qudit, and a superconducting (SC) resonator's electromagnetic field, focusing on the interaction involving both the transition and diagonal dipole moments of the qudit. Specifically, we explore the effective dynamical (time-dependent) longitudinal coupling that arises when a solid-state qudit is adiabatically modulated at small gate frequencies and amplitudes, in addition to a static dispersive interaction with the SC resonator. For the first time, we derive Hamiltonians describing the longitudinal multi-level interactions in a general dispersive regime, encompassing both dynamical longitudinal and dispersive interactions. These Hamiltonians smoothly transition between their adiabatic values, where the couplings of the n-th level are proportional to the level's energy curvature concerning a qudit gate voltage, and the substantially larger dispersive values, which occur due to a resonant form factor.We provide several examples illustrating the transition from adiabatic to dispersive coupling in different qubit systems, including the charge (1e DQD) qubit, the transmon, the double quantum dot singlet-triplet qubit, and the triple quantum dot exchange-only qubit. In some of these qubits, higher energy levels play a critical role, particularly when their qubit's dipole moment is minimal or zero. For an experimentally relevant scenario involving a spin-charge qubit with magnetic field gradient coupled capacitively to a SC resonator, we showcase the potential of these interactions. They enable close-to-quantum-limited quantum non-demolition (QND) measurements and remote geometric phase gates, demonstrating their practical utility in quantum information processing.

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Section: N-level Effective Hamiltonians In Thementioning

confidence: 99%

Modulated longitudinal gates on encoded spin qubits via curvature couplings to a superconducting cavity

Ruskov

Tahan

2021

Phys. Rev. B

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show abstract

“…Treating them as proper quantum multilevel systems can be leveraged in several ways, including enhanced hardware efficiency and functionality of quantum error correction [29,30], faulttolerant protocols [2,31], and versatile quantum simulations with less mapping overhead [32][33][34][35][36]. As a result, the utilization of the higher excited states has recently garnered substantial interest, witnessed through the demonstrations of qutrit operations and algorithms with transmons [21,[37][38][39][40][41][42][43][44][45], other superconducting quantum devices [46,47], as well as trapped ion and photonic platforms [48,49].…”

Section: Introductionmentioning

confidence: 99%

Dissipation and Dephasing of Interacting Photons in Transmon Arrays

Busel¹,

Laine²,

Mansikkamäki³

et al. 2023

Preprint

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Transmon arrays are one of the most promising platforms for quantum information science. Despite being often considered simply as qubits, transmons are inherently quantum mechanical multilevel systems. Being experimentally controllable with high fidelity, the higher excited states beyond the qubit subspace provide an important resource for hardware-efficient many-body quantum simulations, quantum error correction, and quantum information protocols. Alas, dissipation and dephasing phenomena generated by couplings to various uncontrollable environments yield a practical limiting factor to their utilization. To quantify this in detail, we present here the primary consequences of single-transmon dissipation and dephasing to the many-body dynamics of transmon arrays. We use analytical methods from perturbation theory and quantum trajectory approach together with numerical simulations, and deliberately consider the full Hilbert space including the higher excited states. The three main non-unitary processes are many-body decoherence, many-body dissipation, and heating/cooling transitions between different anharmonicity manifolds. Of these, the many-body decoherence -being proportional to the squared distance between the many-body Fock states -gives the strictest limit for observing effective unitary dynamics. Considering experimentally relevant parameters, including also the inevitable site-to-site disorder, our results show that the state-of-theart transmon arrays should be ready for the task of demonstrating coherent many-body dynamics using the higher excited states. However, the wider utilization of transmons for ternary-and-beyond quantum computing calls for improving their coherence properties.

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Longitudinal (curvature) couplings of an N -level qudit to a superconducting resonator at the adiabatic limit and beyond

Ruskov,

Tahan

2024

Phys. Rev. B

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Continuous measurement of a qudit using dispersively coupled radiation

Cited by 8 publications

References 82 publications

Modulated longitudinal gates on encoded spin qubits via curvature couplings to a superconducting cavity

Modulated longitudinal gates on encoded spin qubits via curvature couplings to a superconducting cavity

Dissipation and Dephasing of Interacting Photons in Transmon Arrays

Longitudinal (curvature) couplings of an N -level qudit to a superconducting resonator at the adiabatic limit and beyond

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