Measurement crosstalk between two phase qubits coupled by a coplanar waveguide

Altomare, Fabio; Cicak, Katarina; Sillanpää, Mika; Allman, Michael S.; Sirois, Adam; Li, Dale; Park, Jae I.; Strong, Joshua; Teufel, John; Whittaker, Jed D.; Simmonds, Raymond W.

doi:10.1103/physrevb.82.094510

Cited by 9 publications

(7 citation statements)

References 30 publications

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“…Many of them manifest as dependence of the error process on some external variable, or context, that isn't supposed to affect qubit behavior [22]. For example, an error rate might drift over time [4,[23][24][25], or increase when a nearby qubit is being measured or driven [7][8][9][26][27][28]. These effects are important in their own right.…”

Section: Introductionmentioning

confidence: 99%

Probing Context-Dependent Errors in Quantum Processors

et al. 2019

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Gates in error-prone quantum information processors are often modeled using sets of one-and twoqubit process matrices, the standard model of quantum errors. However, the results of quantum circuits on real processors often depend on additional external "context" variables. Such contexts may include the state of a spectator qubit, the time of data collection, or the temperature of control electronics. In this article we demonstrate a suite of simple, widely applicable, and statistically rigorous methods for detecting context dependence in quantum circuit experiments. They can be used on any data that comprise two or more "pools" of measurement results obtained by repeating the same set of quantum circuits in different contexts. These tools may be integrated seamlessly into standard quantum device characterization techniques, like randomized benchmarking or tomography. We experimentally demonstrate these methods by detecting and quantifying crosstalk and drift on the publicly accessible 16-qubit ibmqx3.

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Section: Introductionmentioning

confidence: 99%

Probing Context-Dependent Errors in Quantum Processors

et al. 2019

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“…Strong resonant coupling of individual qubits [18][19][20] and qubit ensembles [21] to single microwave photons has been achieved. Moreover, cavity-mediated interactions between distant qubits [22][23][24] form the basis for on-chip quantum information processing [25,26] using entangled states of currently up to three qubits [27].…”

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confidence: 99%

Preparation of subradiant states using local qubit control in circuit QED

et al. 2011

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Transitions between quantum states by photon absorption or emission are intimately related to the symmetries of the system which lead to selection rules and the formation of dark states. In a circuit quantum electrodynamics setup, in which two resonant superconducting qubits are coupled through an on-chip cavity and driven via the common cavity field, one single-excitation state remains dark. Here, we demonstrate that this dark state can be excited using local phase control of individual qubit drives to change the symmetry of the excitation field. We observe that the dark state decay via spontaneous emission into the cavity is suppressed, a characteristic signature of subradiance. This local control technique could be used to prepare and study highly correlated quantum states of cavity-coupled qubits.

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“…However, even with a clear understanding of dielectric loss mechanisms [11], long coherence times have been lacking, with all energy relaxation times < 1 µs, apart from one unique device with a crystalline silicon capacitor [9]. Furthermore, phase qubits have relied on tunneling events for state discrimination, which destroys the qubit, creates quasiparticles, and emits broadband microwave radiation crosstalk that can spoil the state of other coupled qubits or cavities [23,[36][37][38]. Although simultaneous qubit measurement [36] has been sufficient for key demonstrations, many of the pitfalls discussed above are difficult to avoid when more than one simultaneous measurement is required.…”

Section: B Rf Squid Phase Qubitsmentioning

confidence: 99%

Tunable-cavity QED with phase qubits

et al. 2014

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We describe a tunable-cavity quantum electrodynamics (QED) architecture with an rf SQUID phase qubit inductively coupled to a single-mode, resonant cavity with a tunable frequency that allows for both microwave readout of tunneling and dispersive measurements of the qubit. Dispersive measurement is well characterized by a three-level model, strongly dependent on qubit anharmonicity, qubit-cavity coupling, and detuning. A tunable-cavity frequency provides a way to strongly vary both the qubit-cavity detuning and coupling strength, which can reduce Purcell losses, cavity-induced dephasing of the qubit, and residual bus coupling for a system with multiple qubits. With our qubit-cavity system, we show that dynamic control over the cavity frequency enables one to avoid Purcell losses during coherent qubit evolutions and optimize state readout during qubit measurements. The maximum qubit decay time T 1 = 1.5 μs is found to be limited by surface dielectric losses from a design geometry similar to planar transmon qubits.

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Measurement crosstalk between two phase qubits coupled by a coplanar waveguide

Cited by 9 publications

References 30 publications

Probing Context-Dependent Errors in Quantum Processors

Probing Context-Dependent Errors in Quantum Processors

Preparation of subradiant states using local qubit control in circuit QED

Tunable-cavity QED with phase qubits

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