Abstract
The superconducting transmon qubit is a leading platform for quantum computing and quantum science. Building large, useful quantum systems based on transmon qubits will require significant improvements in qubit relaxation and coherence times, which are orders of magnitude shorter than limits imposed by bulk properties of the constituent materials. This indicates that relaxation likely originates from uncontrolled surfaces, interfaces, and contaminants. Previous efforts to improve qubit lifetimes have focused primarily on designs that minimize contributions from surfaces. However, significant improvements in the lifetime of two-dimensional transmon qubits have remained elusive for several years. Here, we fabricate two-dimensional transmon qubits that have both lifetimes and coherence times with dynamical decoupling exceeding 0.3 milliseconds by replacing niobium with tantalum in the device. We have observed increased lifetimes for seventeen devices, indicating that these material improvements are robust, paving the way for higher gate fidelities in multi-qubit processors.
Highlights
Steady progress in improving gate fidelities for superconducting qubits over the last two decades has enabled key demonstrations of quantum algorithms[1,2,3], quantum error correction[4,5,6], and quantum supremacy[7]
To determine T1, we excite the qubit with a π-pulse and measure its decay over time at a temperature between 9 and 20 mK
We verify that the deposited tantalum film is in the α phase by measuring resistance as a function of temperature
Summary
Steady progress in improving gate fidelities for superconducting qubits over the last two decades has enabled key demonstrations of quantum algorithms[1,2,3], quantum error correction[4,5,6], and quantum supremacy[7] These demonstrations have relied on either improving coherence through microwave engineering to avoid losses associated with surfaces and interfaces[8,9,10] and to minimize the effects of thermal noise and quasiparticles[11,12,13,14], or by realizing fast gates using tunable coupling[15,16]. We observe a time-averaged T1 exceeding 0.3 ms in our best device and an average T1 of 0.23 ms averaged across all devices, a significant improvement over the state of the art
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