# This Week at Physics

## Events at Physics |
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**R. G. Herb Condensed Matter Seminar**

**High-fidelity entangling gate for double-quantum-dot spin qubits**

**Date:**

**Monday, November 28th**

**Time:**11:00 am

**Place:**5310 Chamberlin Hall

**Speaker:**John Nichol, University of Rochester

**Abstract:**Electron spins in semiconductors are promising qubits, because their long coherence times enable nearly a billion coherent quantum gate operations. However, developing a scalable high-fidelity two-qubit gate remains challenging. We discuss a new entangling gate between two double-quantum-dot spin qubits in GaAs, which uses a magnetic field gradient between the two dots in each qubit to suppress decoherence due to charge noise. When the magnetic gradient dominates the voltage-controlled exchange interaction between electrons, qubit coherence times increase by an order of magnitude. Using randomized benchmarking, we measure single-qubit gate fidelities of approximately 99%, and through self-consistent quantum measurement, state, and process tomography, we measure an entangling gate fidelity of 90%. In the future, operating double quantum dot spin qubits with large gradients in nuclear-spin-free materials, such as Si, should enable a two-qubit gate fidelity surpassing the threshold for fault tolerant quantum information processing.

**Host:**Eriksson