Physical Decoherence Mechanisms
Depolarizing Noise, Pauli Error Model, and Thermal Relaxation describe noise effects — what the state does under imperfection. This note is the physical layer underneath: the actual named causes of decoherence in superconducting hardware (see What is a Quantum Computer).
- Charge noise — fluctuating electric charges near the qubit shift its energy levels.
- Flux noise — fluctuating magnetic flux does the same for flux-sensitive qubit designs.
- Dielectric loss — energy absorbed by imperfections in the insulating materials surrounding the qubit circuit.
- Quasiparticle poisoning — stray unpaired electrons (quasiparticles) breaking the superconducting state locally, causing energy relaxation.
- Crosstalk — unwanted coupling between nominally-independent qubits or control lines, so an operation on one qubit leaks into its neighbors.
Key insight: the toy models elsewhere in this vault (depolarizing/Pauli/thermal) are deliberately agnostic about why — they’re useful precisely because they isolate an effect for study without needing the underlying physics. This note is what those effects are effects of.
Related
- Depolarizing Noise, Pauli Error Model, Thermal Relaxation
- What is a Quantum Computer
- Coherent vs Incoherent Gate Errors
Self-Check
- Could you name the five physical decoherence mechanisms listed here?
- Why do the vault’s toy noise models deliberately avoid specifying a physical cause?
- What’s the difference between quasiparticle poisoning and crosstalk?