Sarah Sheldon

Procedure for systematically tuning up cross-talk in the cross-resonance gate

We present improvements in both theoretical understanding and experimental implementation of the cross resonance (CR) gate that have led to shorter two-qubit gate times and interleaved randomized benchmarking fidelities exceeding 99%. The CR gate is an all-microwave two-qubit gate offers that does not require tunability and is therefore well suited to quantum computing architectures based on 2D superconducting qubits. The performance of the gate has previously been hindered by long gate times and fidelities averaging 94-96%. We have developed a calibration procedure that accurately measures the full CR Hamiltonian. The resulting measurements agree with theoretical analysis of the gate and also elucidate the error terms that have previously limited the gate fidelity. The increase in fidelity that we have achieved was accomplished by introducing a second microwave drive tone on the target qubit to cancel unwanted components of the CR Hamiltonian.

Characterizing errors on qubit operations via iterative randomized benchmarking

With improved gate calibrations reducing unitary errors, we achieve a benchmarked single-qubit gate fidelity of 99.95% with superconducting qubits in a circuit quantum electrodynamics system. We present a method for distinguishing between unitary and non-unitary errors in quantum gates by interleaving repetitions of a target gate within a randomized benchmarking sequence. The benchmarking fidelity decays quadratically with the number of interleaved gates for unitary errors but linearly for non-unitary, allowing us to separate systematic coherent errors from decoherent effects. With this protocol we show that the fidelity of the gates is not limited by unitary errors, but by another drive-activated source of decoherence such as amplitude fluctuations.

Efficient Z gates for quantum computing

For superconducting qubits, microwave pulses drive rotations around the Bloch sphere. The phase of these drives can be used to generate zero-duration arbitrary virtual

Characterization of hidden modes in networks of superconducting qubits

Z

Building quantum logic circuits using arrays of superconducting qubits

gates, which, combined with two

Three Qubit Randomized Benchmarking

{X}_{\ensuremath{\pi}/2}

How do we verify and validate a quantum computer

gates, can generate any SU(2) gate. Here we show how to best utilize these virtual

Correlated randomized benchmarking

Z

Direct tune-up of entangling gates generated by a cross resonance drive

gates to both improve algorithms and correct pulse errors. We perform randomized benchmarking using a Clifford set of Hadamard and

Optimizing gates in the presence of leakage errors

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