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

By S. Sheldon, Easwar Magesan, Jerry M. Chow, Jay M. Gambetta. 2016

430 citations recorded by the source corpus.

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.

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

View Paper: https://www.semanticscholar.org/paper/5f8a54314882a8b59b2e4df41a1ef53af5797380

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Artificial Intelligence

In Atomic and Molecular Physics, and Optics

Citations in the corpus

OpenQASM 3: A Broader and Deeper Quantum Assembly Language (2021, background): “Within a defcal declaration, other calibrations within the defcal scope may be referenced to build up a more sophisticated calibration, as demonstrated with the echoed crossresonance gate below [61].”
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].”
Materials challenges and opportunities for quantum computing hardware (2021, background): “For fixedfrequency transmon qubits, T2,echo ≈ T1 ≈ 100 ms, and typical gate times are around a few hundred nanoseconds (48, 49).”
Universal Gate for Fixed-Frequency Qubits via a Tunable Bus (2016, methodology): “Increasing coherence is less problematic and for coherences measured in comparable devices at IBM T1 = T2 = 80μs [45], gate errors should be < 5 × 10 and competitive with the best reported two-qubit gate errors 9× 10 [12] and 6× 10 [46].”
Demonstration of quantum volume 64 on a superconducting quantum computing system (2020, background): “The CX gate itself can be implemented directly or be created using an echo cross-resonance (ECR) pulse [21] (cf section 5).”
Hardware-efficient variational quantum eigensolver for small molecules and quantum magnets (2017, methodology): “With the addition of single qubit rotations, the CR gate can be used to construct a controlled NOT (CNOT), with fidelities exceeding 99% for gate time ∼ 160 ns [13].”
Error mitigation extends the computational reach of a noisy quantum processor (2018, methodology): “For our ﬁxed-frequency qubits, we use the all-microwave cross-resonance (CR) gate [19, 20], which is implemented by driving a control qubit Q c with a Gaussian-square-modulated microwave pulse that is resonant with the frequency of the target qubit Q t .”
Efficient Z gates for quantum computing (2016, methodology): “Ref [11]) interaction is the example considered in Eqn.”
Laser-annealing Josephson junctions for yielding scaled-up superconducting quantum processors (2020, methodology): “[21] Sheldon, S.”
Supervised learning with quantum-enhanced feature spaces (2018, methodology): “We experimentally veriﬁed our single-and two-qubit unitaries by Randomized Benchmarking (RB) [39, 40] Our two-qubit unitarias are CNOTs constructed from echo cross-resonance sequences [40, 41].”
Tunable Superconducting Qubits with Flux-Independent Coherence (2017, background): “[23,28,29], with a separate microwave port for each readout resonator.”