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arXiv:2603.12900 · Physical review. B./Physical review. B

Photon-mediated entanglement between spin qubits beyond the dispersive regime

Andrei I. Nikitchenko, Guido Burkard

Published Jun 23, 2026• 0 citations
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Abstract

Dispersively coupled distant qubits in a shared cavity can become entangled through virtual photon exchange with energy-conserving phase evolution of their quantum states. This interaction can potentially be accelerated by operating on resonance, allowing for the exchange of real photons. In this theoretical study, we examine photon-mediated entanglement between two distant spins of electrons confined in double quantum dots formed in a Si/SiGe heterostructure. We calculate the dynamics of the combined system comprised of both spin qubits and the cavity, assuming that both spin qubits can be tuned into and out of resonance with the host cavity. We demonstrate that the exchange of real photons between the two spin qubits can result in rapid entanglement that is robust against decoherence. These results pave the way for the development of quantum gates on resonantly coupled distant semiconductor spin qubits.

DOI
10.1103/y6d1-nsxs

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We report the coherent coupling of two electron spins at a distance via virtual microwave photons.Each spin is trapped in a silicon double quantum dot at either end of a superconducting resonator, achieving spinphoton couplings up to around g s =2π ¼ 40 MHz.As the two spins are brought into resonance with each other, but detuned from the photons, an avoided crossing larger than the spin linewidths is observed with an exchange splitting around 2J=2π ¼ 20 MHz.In addition, photon-number states are resolved from the shift 2χ s =2π ¼ -13 MHz that they induce on the spin frequency.These observations demonstrate that we reach the strong dispersive regime of circuit quantum electrodynamics with spins.Achieving spin-spin coupling without real photons is essential to long-range two-qubit gates between spin qubits and scalable networks of spin qubits on a chip.
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