Kvantbittid

Kvantbittid, literally “quantum bit time” in Norwegian and related languages, is a term encountered in some sources to denote the characteristic time scales associated with a quantum bit (qubit). It is not a standard term in English-language quantum computing literature; more common are the concepts of qubit coherence time and gate time. In this usage, kvantbittid encompasses both the duration of qubit operations and the time scales over which a qubit retains quantum information.

Two primary components are gate time and coherence time. Gate time is the duration of a single-qubit operation, such as a rotation. Coherence time describes how long a qubit maintains its quantum state, including T1 (relaxation) and T2 (dephasing), and sometimes T2 when inhomogeneous broadening is relevant. The kvantbittid thus reflects the balance between fast manipulation and maintaining coherence; a shorter gate time relative to coherence times allows more operations before errors accumulate.

Platform examples: In superconducting qubits, gate times are typically tens of nanoseconds, while T1/T2 values are in the tens to hundreds of microseconds. In trapped-ion qubits, gate times are tens to hundreds of microseconds, with coherence times ranging from seconds to minutes under good isolation. Spin qubits in semiconductors can offer nanosecond-to-microsecond gates and microsecond-to-millisecond coherence.

Usage and significance: The concept highlights the performance envelope of a qubit system and is a factor in evaluating fault tolerance and scalability. A common metric is the ratio of coherence time to gate time (the number of possible high-fidelity gates before decoherence). See also qubit, coherence time, gate time, quantum error correction.