Exploiting a Single‐Crystal Environment to Minimize the Charge Noise on Qubits in Silicon

Abstract

Electron spins in silicon offer a competitive, scalable quantum-computing platform with excellent single-qubit properties. However, the two-qubit gate fidelities achieved so far have fallen short of the 99% threshold required for large-scale error-corrected quantum computing architectures. In the past few years, there has been a growing realization that the critical obstacle in meeting this threshold in semiconductor qubits is charge noise arising from the qubit environment. In this work, a notably low level of charge noise of S₀ = 0.0088 ± 0.0004 μeV² Hz^-1 is demonstrated using atom qubits in crystalline silicon, achieved by separating the qubits from surfaces and interface states. The charge noise is measured using both a single electron transistor and an exchange-coupled qubit pair that collectively provide a consistent charge noise spectrum over four frequency decades, with the noise level S₀ being an order of magnitude lower than previously reported. Low-frequency detuning noise, set by the total measurement time, is shown to be the dominant dephasing source of two-qubit exchange oscillations. With recent advances in fast (≈μs) single-shot readout, it is shown that by reducing the total measurement time to ≈1 s, 99.99% two-qubit <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt><mml:mrow><mml:mi>S</mml:mi> <mml:mi>W</mml:mi> <mml:mi>A</mml:mi> <mml:mi>P</mml:mi></mml:mrow> </mml:msqrt> </mml:mrow> </mml:math> gate fidelities can be achieved in single-crystal atom qubits in silicon.