First-principles analysis of cross-resonance gate operation

  title={First-principles analysis of cross-resonance gate operation},
  author={Moein Malekakhlagh and Easwar Magesan and David C. McKay},
  journal={Physical Review A},
We present a comprehensive theoretical study of the cross-resonance gate operation covering estimates for gate parameters and gate error as well as analyzing spectator qubits and multi-qubit frequency collisions. We start by revisiting the derivation of effective Hamiltonian models following Magesan et al. (arXiv:1804.04073). Transmon qubits are commonly modeled as a weakly anharmonic Kerr oscillator. Kerr theory only accounts for qubit frequency renormalization, while adopting number states as… 
Perturbation impact of spectators and spurious qubit interactions on a cross-resonance gate in a tunable coupling superconducting circuit
Cross-resonance (CR) gate has proved to be a promising scheme for implementing fault-tolerant quantum computation with fixed-frequency qubits. In this work, we experimentally implement an entangling
Impact of Spectators on a Two-Qubit Gate in a Tunable Coupling Superconducting Circuit.
This work systematically investigates the dependency of gate fidelities on spurious qubit interactions and presents the first experimental approach to the evaluation of the perturbation impact arising from spectator qubits, and discovers an optimal CR operation regime.
Laser-annealing Josephson junctions for yielding scaled-up superconducting quantum processors
As superconducting quantum circuits scale to larger sizes, the problem of frequency crowding proves a formidable task. Here we present a solution for this problem in fixed-frequency qubit
Supercomputer simulations of transmon quantum computers
A simulator for quantum computers composed of superconducting transmon qubits is developed and a protocol from the theory of quantum error correction and fault tolerance is tested that systematically improves the performance of transmon quantum computers in the presence of characteristic control and measurement errors.
Experimental implementation of non-Clifford interleaved randomized benchmarking with a controlled- S gate
Calibration of a low error non-Clifford Controlled-\frac{\pi}{2}$ phase (CS) gate on a cloud based IBM Quantum computing using the Qiskit Pulse framework is demonstrated.
High-Fidelity Control of Superconducting Qubits Using Direct Microwave Synthesis in Higher Nyquist Zones
This work has incorporated custom superconducting qubit control logic into off-the-shelf hardware capable of low-noise pulse synthesis up to 7.5 GHz using an RF DAC clocked at 5 GHz and enables highly linear and stable microwave synthesis over a wide bandwidth, giving rise to high-resolution control and a reduced number of required signal sources per qubit.
Teaching quantum computing with an interactive textbook
This paper gives an overview of the form taken by the textbook in 2020, a summary of the topics covered and an explanation of the approach taken, and blends traditional text with executable code and interactive elements.
Non-perturbative analytical diagonalization of Hamiltonians with application to coupling suppression and enhancement in cQED
Deriving effective Hamiltonian models plays an essential role in quantum theory, with particular emphasis in recent years on control and engineering problems. In this work, we present two symbolic
Mitigating off-resonant error in the cross-resonance gate
Off-resonant error for a driven quantum system refers to interactions due to the input drives having non-zero spectral overlap with unwanted system transitions. For the cross-resonance gate, this
Continuous quantum gate sets and pulse class meta-optimization
Reducing the circuit depth of quantum circuits is a crucial bottleneck to enabling quantum tech-nology. This depth is inversely proportional to the number of available quantum gates that have been


Operation and intrinsic error budget of a two-qubit cross-resonance gate
We analyze analytically, semi-analytically, and numerically the operation of Cross-Resonance (CR) gate for superconducting qubits (transmons). We find that a relatively simple semi-analytical method
Lifetime renormalization of weakly anharmonic superconducting qubits. I. Role of number nonconserving terms
The dynamics of a weakly anharmonic superconducting qubit in a complex electromagnetic environment is generally well-described by an effective multimode Kerr Hamiltonian at sufficiently weak
Lifetime renormalization of driven weakly anharmonic superconducting qubits. II. The readout problem
Recent experiments in superconducting qubit systems have shown an unexpectedly strong dependence of the qubit relaxation rate on the readout drive power. This phenomenon limits the maximum
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
Effective Hamiltonian models of the cross-resonance gate
Effective Hamiltonian methods are utilized to model the two-qubit cross-resonance gate for both the ideal two-qubit case and when higher levels are included. Analytic expressions are obtained in the
Dispersive regime of circuit QED : Photon-dependent qubit dephasing and relaxation rates
Superconducting electrical circuits can be used to study the physics of cavity quantum electrodynamics (QED) in new regimes, therefore realizing circuit QED. For quantum-information processing and
Optimized cross-resonance gate for coupled transmon systems
The cross-resonant gate is an entangling gate for fixed frequency superconducting qubits introduced for untunable qubits. While being simple and extensible, it suffers from long duration and limited
Fully microwave-tunable universal gates in superconducting qubits with linear couplings and fixed transition frequencies
A register of quantum bits with fixed transition frequencies and weakly coupled to one another through simple linear circuit elements is an experimentally minimal architecture for a small-scale
Coupling superconducting qubits via a cavity bus
These experiments show that two nearby qubits can be readily coupled with local interactions, and show the implementation of a quantum bus, using microwave photons confined in a transmission line cavity, to couple two superconducting qubits on opposite sides of a chip.
Cutoff-Free Circuit Quantum Electrodynamics.
It is shown here that unless gauge invariance is respected, any attempt at the calculation of circuit QED quantities is bound to diverge and a theoretical approach is presented to the calculations of a finite spontaneous emission rate and the Lamb shift that is free of cutoff.