Spin-transparent storage rings as a quantum computing architecture

Charged particles in spin-transparent storage rings can exhibit long spin-coherence times of up to several hours, making them an interesting but untested prospect for quantum computing. Several of the critical requirements of quantum computing have been experimentally achieved: State-preparation is done by shining polarized light on a photocathode, emitting spin-polarized electrons. Single-qubit gates are performed by the arbitrary polarization rotations implemented by the pulsed magnetic field of a solenoid. Finally, readout of the spin-polarization state is done using a Mott-polarimeter. The remaining necessary ingredient for universal quantum computing is a way to perform two-qubit gates. While performing two-qubit operations on particles in the storage ring appears challenging, we have identified a possible scheme to load electrons with entangled spins by generating them with an entangled train of light pulses on the photocathode. These spin-entangled electrons could then be used as a resource in a measurement-based scheme to perform multi-qubit gates in the storage ring.