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What is decoherence?
Decoherence is a qubit gradually losing its superposition and entanglement, its quantum properties, through unwanted interaction with its environment.
Real qubits cannot be perfectly isolated: heat, electromagnetic noise and material defects disturb the qubit’s state. How long a qubit keeps its information is usually measured by the T1 (energy loss) and T2 (phase loss) times.
For superconducting qubits these times are typically tens to hundreds of microseconds today. A circuit has to finish within this time; longer computations require quantum error correction.
Related packages
- Qiskit Aer ile gürültülü kuantum simülasyonu
- QuTiP: açık kuantum sistemleri simülasyonu
- scqubits ile süperiletken kübit (transmon) fiziği
Related concepts
- Quantum error correction · Quantum error correction spreads one logical qubit over many physical qubits so that errors caused by noise can be found and fixed without measuring the qubits directly.
- NISQ (noisy intermediate-scale quantum) · NISQ is the current era of quantum computing, named by John Preskill in 2018: devices with tens to a few hundred noisy qubits and no error correction.
- Quantum measurement · Quantum measurement ends a qubit’s superposition and returns 0 or 1, with the result chosen at random according to the amplitudes.