How to Bias Multiple Quantum Qubits

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Precision Source / Measure Unit
+ Precision Source / Measure Unit
Precision Source / Measure Unit
+ Precision Source / Measure Unit

Minimizing bias voltage fluctuations to prevent decoherence

Characterizing qubit properties requires precision control and evaluation systems to initialize, control, and read qubits. The system enables the characterization of qubit properties, such as coherence time and fidelity, while maintaining the integrity of the qubits. The DC voltage bias source is one of the most critical aspects in the qubit control and evaluation system for flux-tunable superconducting qubits and silicon spin qubits. Using low-noise power supplies, source meters, and source measure units (SMUs) are essential to minimizing bias voltage fluctuations. The clean bias voltage position must be as close as possible to the cryostat to maintain the integrity of qubit states, ensuring accurate and reliable quantum information processing. This approach can significantly help with unnecessary environmental interference caused by exposed cable lengths.

Using a high-precision source measure unit and a low-noise filter can further minimize voltage noise. Employing different grounds for each instrument can create a circuit known as a ground loop, which can be a source of noise. Techniques such as single-point grounding are necessary to avoid ground loops. Experiment with the LF terminal configurations, such as floating or frame grounding, to understand the impact of the noise level of the DC bias voltage. Choose the one that yields better results. Noise from electromagnetic induction can occur if the high-frequency (HF) and long-frequency (LF) cables become spatially separated. Keep the HF and LF cables as close as possible, or use a twisted pair configuration to prevent this from occurring.

Quantum qubit control solution

Providing stable and clean DC bias voltage to more than 100 qubits requires a combination of source meter options with a high channel density, low noise, and precision voltage supply. The Keysight quantum qubit control solution integrates 100 precision power supply channels into a 5U height of the full rack-width space. The solution enables positioning near the cryostat due to its compact form factor, reducing qubit decoherence from environmental interference due to long exposed cables. This platform includes low-noise filter adapters (LNF) to push the stability of the bias voltage further.
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