Rapid high-fidelity multiplexed readout of superconducting qubits (1801.07904v1)

Published 24 Jan 2018 in quant-ph

Abstract: The duration and fidelity of qubit readout is a critical factor for applications in quantum information processing as it limits the fidelity of algorithms which reuse qubits after measurement or apply feedback based on the measurement result. Here we present fast multiplexed readout of five qubits in a single 1.2 GHz wide readout channel. Using a readout pulse length of 80 ns and populating readout resonators for less than 250 ns we find an average correct assignment probability for the five measured qubits to be $97\%$. The differences between the individual readout errors and those found when measuring the qubits simultaneously are within $1\%$. We employ individual Purcell filters for each readout resonator to suppress off-resonant driving, which we characterize by the dephasing imposed on unintentionally measured qubits. We expect the here presented readout scheme to become particularly useful for the selective readout of individual qubits in multi-qubit quantum processors.

Citations (201)

View on Semantic Scholar

Summary

Essay: Rapid High-Fidelity Multiplexed Readout of Superconducting Qubits

The paper at hand presents a notable paper in the domain of quantum information processing by focusing on the advancement of rapid, high-fidelity readout of superconducting qubits. The authors introduce a multiplexed readout architecture designed to enable simultaneous readout of multiple qubits within a constrained bandwidth, showing impressive correct assignment probabilities even with fast measurement protocols. The fidelity and speed of qubit readout are crucial for efficient quantum computations, especially as algorithms grow to require more extensive use of qubit measurements.

Technical Achievements

The paper showcases a method for the fast multiplexed readout of five qubits using a single readout channel with a bandwidth of 1.2 GHz. By employing an 80 ns readout pulse, the authors achieve an average correct assignment probability of 97% across the five qubits. This performance metric represents a significant contribution to superconducting qubit technologies, particularly notable due to the minimal crosstalk observed when multiple qubits are read out simultaneously. The distinctions between the individual and collective readout errors remain within 1%, suggesting minimal disruptions or inaccuracies introduced by multiplexing.

A unique aspect of this method is the application of individual Purcell filters for each readout resonator. The filters are instrumental in suppressing off-resonant driving, primarily by attenuating unwanted resonant excitations that could lead to qubit dephasing. This configuration facilitates a reduction in measurement-induced dephasing, which is crucial for maintaining the coherence of other qubits in a quantum processor during selective readout operations.

Practical and Theoretical Implications

The implications of these advancements are substantial both practically and theoretically. From a practical viewpoint, this multiplexed readout scheme simplifies device architecture and enhances resource efficiency, allowing for more qubits to be read without corresponding increases in control hardware complexity. These improvements are poised to benefit scalable quantum computing estimates as larger quantum systems are pursued.

Theoretically, the successful demonstration of low crosstalk and high fidelity in the multiplexed readout process provides an empirical basis for examining more complex readout architectures, potentially leading to more generalized models of qubit interactions and state-readout dynamics under multiplexed conditions. Furthermore, the resonator configurations and individual qubit protection strategies introduced here offer a schematic blueprint for integrating Purcell filters in quantum error-correcting codes, such as those necessary in the surface code application.

Future Developments

Looking forward, one may speculate about multiple future trajectories that this line of research might take in artificial intelligence and quantum computing. The extension of these concepts to larger qubit systems with minimal crosstalk and enhanced fidelity could redefine the operational paradigms of error correction algorithms or iterative quantum algorithms (e.g., quantum Fourier transform). These advancements, combined with better materials and fabrication techniques for superconducting circuits, could tremendously improve qubit coherence times and readout efficiencies.

The authors emphasize the influence of probe pulse shaping, which indicates potential avenues to further minimize dephasing through refined control over readout pulses. Such developments could facilitate even closer integration of quantum computing infrastructure with current classical computation frameworks, potentially bolstering the overall quantum-classical hybrid computing systems' capabilities.