Qubits and quantum devices
Can ordinary silicon host fast, accurate spin qubits?
Open access · cc by · source: Europe PMC
A carefully designed tiny magnet let electron spins in ordinary (non-purified) silicon be flipped fast enough and cleanly enough to pass the error threshold for fault-tolerant quantum computing.
Study at a glance
- Design
- Other — Low-temperature device experiment on a Si/SiGe double quantum dot with a cobalt micromagnet, driven by electric dipole spin resonance
- N
- One device; most data are from the left dot, with the right dot showing similar results in the supplement
- Population
- Single electron spins in a natural-silicon Si/SiGe double quantum dot at about 120 mK
- Outcome
- Rabi frequency, Rabi decay time, dephasing time T2*, quality factor Q and single-qubit Clifford gate fidelity
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
The two dots' resonances were split by about 800 MHz, so each spin could be addressed with negligible crosstalk (about 0.02% on the idle qubit). The dephasing time T2* was 1.83 μs, the longest reported for natural-silicon dot qubits, and Rabi frequencies reached about 35 MHz at maximum drive. The best trade-off between speed and decay was near a 10 MHz Rabi frequency with a quality factor of about 140, where the average single-qubit Clifford gate fidelity was 99.6%. Stronger driving shortened the decay time, which the authors attribute mainly to microwave heating.
Methodology
The team built a double quantum dot in a natural Si/SiGe heterostructure, each dot holding one electron, and placed a cobalt micromagnet on top to create a strong magnetic field gradient. Microwaves applied to a gate shake the electron in this gradient, which acts like an oscillating magnetic field that rotates the spin (electric dipole spin resonance). They measured resonance spectra, Rabi oscillations, Ramsey fringes, how driving strength affects speed and decay, and finally gate fidelity by randomized benchmarking.
Limitations
Only single-qubit operations are shown; a two-qubit gate, which is needed for real computation, is proposed but not demonstrated. The results come from one device, and detailed data mostly from one of the two dots because the charge sensor was more sensitive to it. The heating explanation for faster decay at high drive is inferred rather than measured directly, and nuclear-spin noise from natural silicon still limits dephasing.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Silicon's low nuclear-spin noise gives long coherence.
Silicon spin qubits reach microsecond dephasing times: a natural-silicon double dot had T2* = 1.83 µs and 99.6% single-qubit Clifford fidelity, and an isotopically enhanced triple dot reached 2.31 µs versus about 10 ns in GaAs.
Evidence for the claim as stated.
Silicon's low nuclear-spin noise gives long coherence.
Silicon spin qubits reach microsecond dephasing times: a natural-silicon double dot had T2* = 1.83 µs and 99.6% single-qubit Clifford fidelity, and an isotopically enhanced triple dot reached 2.31 µs versus about 10 ns in GaAs.
Scope note — Single-qubit gates only; one device.
Limits the claim's scope: a different population, assay, or outcome.
Knowing the dominant noise source guides what to fix.
Remaining noise is often not nuclear: the triple-dot device's magnetic noise appeared to come from electronic paramagnetism, with 1/f charge noise near 15 µV, and in the natural-silicon device faster driving shortened decay, attributed to microwave heating.
Evidence for the claim as stated.
Platform differences: spin-qubit studies measure dephasing and single-qubit fidelity on single devices, whereas transmon work reports processor-scale two-qubit fidelities; the numbers are not directly comparable across platforms.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
Platform differences: spin-qubit studies measure dephasing and single-qubit fidelity on single devices, whereas transmon work reports processor-scale two-qubit fidelities; the numbers are not directly comparable across platforms.
Discoveries this paper informs or conflicts with
- Silicon spin qubits reached microsecond coherence both with and without isotope purification
This paper informs this development.
Related papers in this topic
Same topic cluster — not a recommendation engine.