Transmons are widely adopted in quantum computing architectures for their engineered insensitivity to charge noise and correspondingly long relaxation times. Despite this advantage, transmons often exhibit large fluctuations in dephasing times across different devices and also within qubits on the same device. Existing transmon qubits are assumed to be insensitive to charge noise. However, very little recent attention has been paid to the dependence of dephasing on the local charge environment. In this study, we see fluctuations in the dephasing time, $T_ϕ$ , which correlate to charge offset. While charge offset fluctuations are slow, parity switches are fast processes tied to the charge offset and can affect $T_ϕ$ in Ramsey experiments. We implement a protocol to detect parity switching events using single-shot methods, which are interleaved within a Ramsey measurement. We find that events that remain in the same parity state have a higher $T_2$ than measurements averaged over both parities. Our results show that transmons can be limited by charge-noise, even with $E_\text{J}/E_\text{C} \approx 50$ . Consequently, parity flip rates must be considered as a device characterization metric.Transmons are widely adopted in quantum computing architectures for their engineered insensitivity to charge noise and correspondingly long relaxation times. Despite this advantage, transmons often exhibit large fluctuations in dephasing times across different devices and also within qubits on the same device. Existing transmon qubits are assumed to be insensitive to charge noise. However, very little recent attention has been paid to the dependence of dephasing on the local charge environment. In this study, we see fluctuations in the dephasing time, $T_ϕ$, which correlate to charge offset. While charge offset fluctuations are slow, parity switches are fast processes tied to the charge offset and can affect $T_ϕ$ in Ramsey experiments. We implement a protocol to detect parity switching events using single-shot methods, which are interleaved within a Ramsey measurement. We find that events that remain in the same parity state have a higher $T_2$ than measurements averaged over both parities. Our results show that transmons can be limited by charge-noise, even with $E_\text{J}/E_\text{C} \approx 50$. Consequently, parity flip rates must be considered as a device characterization metric.

arXiv:2508.03973Aug 5, 20250 citations

Quantum Computing with Transmon Qubits

Maika Takita

The Japan Society of Applied PhysicsJan 28, 20200 citations

Suppressing charge noise decoherence in superconducting charge qubits

J. A. Schreier, Andrew Houck, Jens Koch +9 more

We present an experimental realization of the transmon qubit, which is an improved superconducting charge qubit derived from the Cooper pair box. We experimentally verify the predicted exponential suppression of sensitivity to $1∕f$ charge noise. This removes the leading source of dephasing in charge qubits which results in homogeneously broadened transitions with relaxation and dephasing times in the microsecond range. Our systematic characterization of the qubit spectrum, anharmonicity, and charge dispersion shows excellent agreement with theory.We present an experimental realization of the transmon qubit, which is an improved superconducting charge qubit derived from the Cooper pair box. We experimentally verify the predicted exponential suppression of sensitivity to $1∕f$ charge noise. This removes the leading source of dephasing in charge qubits which results in homogeneously broadened transitions with relaxation and dephasing times in the microsecond range. Our systematic characterization of the qubit spectrum, anharmonicity, and charge dispersion shows excellent agreement with theory.

arXiv:0712.3581Physical Review BMay 12, 2008552 citations

Decoherence in Improved Transmon Qubits

Adam Sears, Hanhee Paik, David Schuster +5 more

Bulletin of the American Physical SocietyMar 25, 20110 citations

T_ϕ

, which correlate to charge offset. While charge offset fluctuations are slow, parity switches are fast processes tied to the charge offset and can affect

T_ϕ

in Ramsey experiments. We implement a protocol to detect parity switching events using single-shot methods, which are interleaved within a Ramsey measurement. We find that events that remain in the same parity state have a higher

T_2

than measurements averaged over both parities. Our results show that transmons can be limited by charge-noise, even with

E_\text{J}/E_\text{C} \approx 50

. Consequently, parity flip rates must be considered as a device characterization metric.

1∕f

charge noise. This removes the leading source of dephasing in charge qubits which results in homogeneously broadened transitions with relaxation and dephasing times in the microsecond range. Our systematic characterization of the qubit spectrum, anharmonicity, and charge dispersion shows excellent agreement with theory.