paper / andreaswallraff / Feb 5
Tantalum-based superconducting qubits, while offering reduced dielectric losses, exhibit significant sensitivity to infrared radiation, unlike niobium-based qubits. This IR sensitivity contributes markedly to decoherence in tantalum systems, necessitating targeted filtering. The observed time-dependent tunneling rates suggest slowly cooling components in experimental setups introduce radiant thermal noise, highlighting the critical need to address radiative backgrounds in future qubit platform designs for improved coherence.
superconducting-qubitsquantum-computinginfrared-radiationdecoherenceniobium-tantalumquasiparticles
“Tantalum-based superconducting qubits are significantly more sensitive to infrared radiation than niobium-based qubits.”
paper / andreaswallraff / Jul 21
Cross-platform verification — confirming that separate quantum modules prepare identical quantum states — is a prerequisite for modular quantum computing scalability, but classical-communication-only protocols scale exponentially in qubit count. This work demonstrates on a six-qubit flip-chip superconducting device (two 3-qubit modules) that introducing a single inter-module two-qubit gate breaks the exponential scaling barrier, achieving sub-exponential resource requirements. The practical payoff is a 4× reduction in required measurement repetitions for 3-qubit states, with greater gains projected as system size and fidelity increase.
quantum-computingmodular-architecturesuperconducting-qubitsquantum-verificationbenchmarkingcross-platformquantum-hardware
“Cross-platform verification protocols that rely solely on classical communication between modules scale exponentially with qubit number.”
paper / andreaswallraff / Mar 16
This paper details the development and characterization of a multi-chip module for superconducting quantum processors, mitigating limitations of monolithic designs. The architecture integrates multiple qubit modules with a carrier chip, utilizing 3D integration to enhance scalability and performance. Key findings include low state-assignment errors, high-fidelity single-qubit gates, and successful implementation of a controlled-Z two-qubit gate via static inter-module couplers, demonstrating a path toward larger and more robust quantum systems. This work advances modular quantum computing by achieving high operational performance across interconnected chips.
quantum-computingsuperconducting-qubitsmulti-chip-modulequantum-processor-performancequbit-integrationquantum-error-correctionquantum-information
“Modular architectures improve scalability and performance of superconducting quantum processors.”
paper / andreaswallraff / Mar 14
This work demonstrates a continuous set of controlled arbitrary-phase (CZθ) gates on flux-tunable transmon qubits. The implementation achieves robustness against control pulse distortions and utilizes a single idle time parameter for continuous gate tuning. The proposed methods for calibration and benchmarking, including a novel leakage measurement and cross-entropy benchmarking cycle, are broadly applicable across quantum computing.
quantum-computingquantum-algorithmsquantum-gatestransmon-qubitsquantum-error-correctionquantum-benchmarking
“A continuous set of controlled arbitrary-phase (CZθ) gates was demonstrated on flux-tunable transmon qubits.”
paper / andreaswallraff / Mar 6
Accurate and fast magnetic flux control is crucial for high-fidelity two-qubit gates and reduced readout errors in superconducting quantum computing. This work presents a novel calibration method that compensates for flux control line distortions across nanosecond to microsecond timescales, achieving sub-permille residual frequency errors. This advancement is critical for scaling up superconducting quantum processors by enabling reliable qubit operation and gate calibration.
quantum-computingsuperconducting-circuitsmagnetic-flux-controlqubit-calibrationquantum-error-correctionnanosecond-pulses
“Precise magnetic flux tuning is essential for high-fidelity two-qubit gates and minimizing readout errors in superconducting qubits.”