Coherent spin-spin coupling mediated by virtual microwave photons

Harvey-Collard, Patrick; Dijkema, Jurgen; Zheng, Guoji; Sammak, Amir; Scappucci, Giordano; Vandersypen, Lieven M. K.

doi:10.48550/arxiv.2108.01206

Cited by 5 publications

(11 citation statements)

References 39 publications

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“…Despite the fact that hybrid spin qubits are more prone to charge noise, references [34,35] have achieved the strong coupling regime, i.e., the spin-photon coupling rate is greater than the spin decoherence rate and the cavity loss rate. Recently, Borjans et al [37], demonstrated that one can coherently couple two spin qubits with a resonator by extending the architecture in [34] and Harvey-Collard et al [38] reported the coupling of distant spins through virtual photons. The latter represents a significant step towards the experimental realisation of cavity-mediated two-qubit gates.…”

Section: A Overviewmentioning

confidence: 99%

Multicore Quantum Computing

Jnane,

Undseth,

Cai

et al. 2022

Preprint

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Any architecture for practical quantum computing must be scalable. An attractive approach is to create multiple cores, computing regions of fixed size that are well-spaced but interlinked with communication channels. This exploded architecture can relax the demands associated with a single monolithic device: the complexity of control, cooling and power infrastructure as well as the difficulties of cross-talk suppression and near-perfect component yield. Here we explore interlinked multicore architectures through analytic and numerical modelling. While elements of our analysis are relevant to diverse platforms, our focus is on semiconductor electron spin systems in which numerous cores may exist on a single chip. We model shuttling and microwave-based interlinks and estimate the achievable fidelities, finding values that are encouraging but markedly inferior to intra-core operations. We therefore introduce optimsed entanglement purification to enable highfidelity communication, finding that 99.5% is a very realistic goal. We then assess the prospects for quantum advantage using such devices in the NISQ-era and beyond: we simulate recently proposed exponentially-powerful error mitigation schemes in the multicore environment and conclude that these techniques impressively suppress imperfections in both the inter-and intra-core operations.

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Section: A Overviewmentioning

confidence: 99%

Multicore Quantum Computing

Jnane,

Undseth,

Cai

et al. 2022

Preprint

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“…By using nuclear spin-free 28 Si [3], the spin qubit dephasing time is significantly increased, as it is no longer limited by hyperfine interaction with remaining 29 Si, but by charge noise, which couples via local magnetic field gradients [4][5][6][7]. The fidelity of single-qubit [5,[8][9][10] and two-qubit gates [11] already exceeds the quantum error correction threshold [12]. Simple two-qubit gates require an overlap of the electron wave-function [13][14][15], which would require a very dense two-dimensional qubit matrix, in which topological quantum error correction can be realized [16,17].…”

Section: Introductionmentioning

confidence: 99%

Blueprint of a scalable spin qubit shuttle device for coherent mid-range qubit transfer in disordered Si/SiGe/SiO$_2$

Langrock¹,

Krzywda²,

Focke³

et al. 2022

Preprint

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Silicon spin qubits stand out due to their very long coherence times, compatibility with industrial fabrication, and prospect to integrate classical control electronics. To achieve a truly scalable architecture, a coherent mid-range link between qubit registers has been suggested to solve the signal fan-out problem. Here we present a blueprint of such a ∼ 10 µm long link, called a spin qubit shuttle, which is based on connecting an array of gates into a small number of sets. The number of these gate sets and thus the number of required control signal is independent of the link distance to coherently shuttle the electron qubit. We discuss two different operation modes for the spin qubit shuttle: A qubit conveyor, i.e. a potential minimum that smoothly moves laterally, and a bucket brigade, in which the electron is transported through a series of tunnel-coupled quantum dots by adiabatic passage. We find the former approach more promising considering a realistic Si/SiGe device including potential disorder from the charged defects at the Si/SiO2 layer, as well as typical charge noise. Focusing on the qubit transfer fidelity of the conveyor shuttling mode, motional narrowing, the interplay between orbital and valley excitation and relaxation in presence of g-factors that depend on orbital and valley state of the electron, and effects from spin-hotspots are discussed in detail. We find that a transfer fidelity of 99.9 % is feasible in Si/SiGe at a speed of ∼10 m/s, if the average valley splitting and its inhomogeneity stay within realistic bounds. Operation at low global magnetic field ≈ 20 mT and material engineering towards high valley splitting is favourable to reach high transfer fidelities.

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“…Driven by significant technological progress in enhancing the amplitude of spin-photon interactions [42][43][44], coupling distant spin qubits via microwave resonators is an appealing approach [45]. In analogy to superconducting circuits [46,47], current spin-photon interfaces are designed to be transversal, where nearly resonant photons flip the spin state.…”

mentioning

confidence: 99%

Fully tunable longitudinal spin-photon interactions in Si and Ge quantum dots

Bosco,

Scarlino,

Klinovaja

et al. 2022

Preprint

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Spin qubits in silicon and germanium quantum dots are promising platforms for quantum computing, but entangling spin qubits over micrometer distances remains a critical challenge. Current prototypical architectures maximize transversal interactions between qubits and microwave resonators, where the spin state is flipped by nearly resonant photons. However, these interactions cause back-action on the qubit, that yield unavoidable residual qubit-qubit couplings and significantly affect the gate fidelity. Strikingly, residual couplings vanish when spin-photon interactions are longitudinal and photons couple to the phase of the qubit. We show that large longitudinal interactions emerge naturally in state-of-the-art hole spin qubits. These interactions are fully tunable and can be parametrically modulated by external oscillating electric fields. We propose realistic protocols to measure these interactions and to implement fast and high-fidelity two-qubit entangling gates. These protocols work also at high temperatures, paving the way towards the implementation of large-scale quantum processors.

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Coherent spin-spin coupling mediated by virtual microwave photons

Cited by 5 publications

References 39 publications

Multicore Quantum Computing

Multicore Quantum Computing

Blueprint of a scalable spin qubit shuttle device for coherent mid-range qubit transfer in disordered Si/SiGe/SiO$_2$

Fully tunable longitudinal spin-photon interactions in Si and Ge quantum dots

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