Reducing Unitary and Spectator Errors in Cross Resonance with Optimized Rotary Echoes

By N. Sundaresan, I. Lauer, E. Pritchett, Easwar Magesan, P. Jurcevic, Jay M. Gambetta. 2020

148 citations recorded by the source corpus.

We present an improvement to the cross resonance gate realized with the addition of resonant, target rotary pulses. These pulses, applied directly to the target qubit, are simultaneous to and in phase with the echoed cross resonance pulses. Using specialized Hamiltonian error amplifying tomography, we confirm a reduction of error terms with target rotary -- directly translating to improved two-qubit gate fidelity. Beyond improvement in the control-target subspace, the target rotary reduces entanglement between target and target spectators caused by residual quantum interactions. We further characterize multi-qubit performance improvement enabled by target rotary pulsing using unitarity benchmarking and quantum volume measurements, achieving a new record quantum volume for a superconducting qubit system.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/188d6415067a34d2e5b86562172f6b69ddcfe53d

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In Artificial Intelligence

In Atomic and Molecular Physics, and Optics

Citations in the corpus

Quantum optimal control in quantum technologies. Strategic report on current status, visions and goals for research in Europe (2022, methodology): “The response of the system to specific measurement sequences is used to iteratively find optimal parameter values for single-qubit [516] or two-qubit gate operations [517, 543] involving automatic protocols [627].”
Suppression of Crosstalk in Superconducting Qubits Using Dynamical Decoupling (2021, methodology): “The Quito CNOT gate is based on the “echo cross-resonance” (CR) gate [45], which consists of two CR pulses on the control qubit, two rotary pulses on the target qubit [46], and several single qubit gates.”
OpenQASM 3: A Broader and Deeper Quantum Assembly Language (2021, background): “Consider for example a rotation called rotary that is applied for the entire duration of some other gate [75].”
Demonstration of quantum volume 64 on a superconducting quantum computing system (2020, methodology): “In section 2 we give an overview of the ibmq_montreal device, which is a 27-qubit IBM Quantum Falcon processor; in section 3 we discuss the improvements to the compiler; in section 4 we discuss the dynamical decoupling protocol; in section 5 we discuss the faster implementation of the direct CNOT ga”