Quantification and characterization of leakage errors

Wood, Christopher J.; Gambetta, Jay

doi:10.1103/physreva.97.032306

Cited by 116 publications

(104 citation statements)

References 35 publications

(72 reference statements)

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“…and this indirect interaction of qubits (last term) is used for the CZ gate. The quantum map E can be derived solving by the Lindblad master equation, and then we calculate the average gate (in)fidelity in the computational subspace |ψ s between the map E and an ideal CZ gate map E CZ , which is defined as [33,34] F(E,…”

Section: Appendix a Using The Rotated Lattice For Logical Qubit Encomentioning

confidence: 99%

Pseudo-2D superconducting quantum computing circuit for the surface code: proposal and preliminary tests

et al. 2020

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Among the major hardware platforms for large-scale quantum computing, one of the leading candidates is superconducting quantum circuits. Current proposed architectures for quantum error-correction with the promising surface code require a two-dimensional layout of superconducting qubits with nearest-neighbor interactions. A major hurdle for the scalability in such an architecture using superconducting systems is the so-called wiring problem, where qubits internal to a chipset become difficult to access by the external control/readout lines. In contrast to the existing approaches which address the problem through intricate three-dimensional wiring and packaging technology, leading to a significant engineering challenge, here we address this problem by presenting a modified microarchitecture in which all the wiring can be realized through a newly introduced pseudo two-dimensional resonator network which provides the inter-qubit connections via airbridges. Our proposal is completely compatible with current standard planar circuit technology. We carried out experiments to examine the feasibility of the new airbridge component. The measured quality factor of the airbridged resonator is below the simulated surface-code threshold required for a coupling resonator, and it should not limit simulated gate fidelity. The measured crosstalk between crossed resonators is at most −49 dB in resonance. Further spatial and frequency separation between the resonators should result in relatively limited crosstalk between them, which would not increase as the size of the chipset increases. This architecture and the preliminary tests indicate the possibility that a large-scale, fully error-corrected quantum computer could be constructed by monolithic integration technologies without additional overhead or special packaging know-how.

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Section: Appendix a Using The Rotated Lattice For Logical Qubit Encomentioning

confidence: 99%

Pseudo-2D superconducting quantum computing circuit for the surface code: proposal and preliminary tests

et al. 2020

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“…However, the particular choice to center around an error-rate of 10 4 is motivated by spontaneous Raman scattering rates in ion traps. It has been estimated that a 200-500 s m gate experiences a spontaneous scattering event with probability 10 to 10 4 3 -- [31,77], and each spontaneous scattering event can populate any state with approximately equal probability. For qubits based on clock transitions, this splits between the two computational states, as well as two leakage states formed by Zeeman splitting.…”

Section: Leakage Simulationsmentioning

confidence: 99%

Handling leakage with subsystem codes

2019

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Leakage is a particularly damaging error that occurs when a qubit state falls out of its two-level computational subspace. Compared to independent depolarizing noise, leaked qubits may produce many more configurations of harmful correlated errors during error-correction. In this work, we investigate different local codes in the low-error regime of a leakage gate error model. When restricting to bare-ancilla extraction, we observe that subsystem codes are good candidates for handling leakage, as their locality can limit damaging correlated errors. As a case study, we compare subspace surface codes to the subsystem surface codes introduced by Bravyi et al. In contrast to depolarizing noise, subsystem surface codes outperform same-distance subspace surface codes below error rates as high as 7.5×10 −4 while offering better per-qubit distance protection. Furthermore, we show that at low to intermediate distances, Bacon-Shor codes offer better per-qubit error protection against leakage in an ion-trap motivated error model below error rates as high as 1.2×10 −3 . For restricted leakage models, this advantage can be extended to higher distances by relaxing to unverified two-qubit cat state extraction in the surface code. These results highlight an intrinsic benefit of subsystem code locality to error-corrective performance.

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“…This process is usually modeled as irreversible and incoherent, in which case the qubit has no effect on any subsequent operation. More realistically, qubit operations create and manipulate superpositions of computational and non-computational states [26]. In such cases a qubit can effectively leave and later return to the computational subspace, interfering with the computational evolution.…”

Section: Coherent Qubit Leakagementioning

confidence: 99%

“…The development of QPI was motivated by studies addressing the limitations of GST and RB for processes with non-Markovian aspects [5,[23][24][25] and by the emergence of ad-hoc adaptations of these methods to characterize specific types of non-Markovian errors [13,26]. QPI provides a general, systematic solution to these challenges.…”

Section: Introductionmentioning

confidence: 99%

Quantum process identification: a method for characterizing non-markovian quantum dynamics

Bennink

Lougovski

2019

New J. Phys.

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Established methods for characterizing quantum information processes do not capture non-Markovian (history-dependent) behaviors that occur in real systems. These methods model a quantum process as a fixed map on the state space of a predefined system of interest. Such a map averages over the system's environment, which may retain some effect of its past interactions with the system and thus have a history-dependent influence on the system. Although the theory of non-Markovian quantum dynamics is currently an active area of research, a systematic characterization method based on a general representation of non-Markovian dynamics has been lacking. In this article we present a systematic method for experimentally characterizing the dynamics of open quantum systems. Our method, which we call quantum process identification (QPI), is based on a general theoretical framework which relates the (non-Markovian) evolution of a system over an extended period of time to a time-local (Markovian) process involving the system and an effective environment. In practical terms, QPI uses time-resolved tomographic measurements of a quantum system to construct a dynamical model with as many dynamical variables as are necessary to reproduce the evolution of the system. Through numerical simulations, we demonstrate that QPI can be used to characterize qubit operations with non-Markovian errors arising from realistic dynamics including control drift, coherent leakage, and coherent interaction with material impurities.

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Quantification and characterization of leakage errors

Cited by 116 publications

References 35 publications

Pseudo-2D superconducting quantum computing circuit for the surface code: proposal and preliminary tests

Pseudo-2D superconducting quantum computing circuit for the surface code: proposal and preliminary tests

Handling leakage with subsystem codes

Quantum process identification: a method for characterizing non-markovian quantum dynamics

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