dephase

Dephase is a term used to describe the process by which components of a system lose their fixed phase relationship with one another, leading to a reduction in coherence. In physics and engineering, dephasing typically refers to the randomization of relative phases due to interactions with an environment, rather than a transfer of energy.

In quantum systems, dephasing is a key source of decoherence that affects superposition states and interference phenomena. The loss of phase coherence is characterized by a dephasing time, often denoted T2. In many contexts, total dephasing arises from both energy relaxation (trait of T1 processes) and pure dephasing, with the relation 1/T2 = 1/(2T1) + 1/Tphi, where Tphi is the pure dephasing time. Dephasing can result from fluctuations in the environment, such as magnetic or electric field noise, thermal phonons, or charge noise, and it reduces the visibility of quantum interference without necessarily changing the energy of the system.

In optics and related fields, dephasing describes the loss of fixed phase between light waves or between components of a driven field. Phase fluctuations or dispersion can broaden spectral lines and shorten coherence time, affecting applications like interferometry and coherent light generation. In electronic and spin-based technologies, dephasing limits the performance of devices that rely on coherent superpositions, including certain quantum bits (qubits) and spintronic components.

Mitigation strategies include isolating systems from noise, dynamical decoupling and echo techniques, operating at low temperatures, material purification, and error correction in quantum information contexts. Dephasing is distinguished from broader decoherence by its emphasis on phase relationships rather than energy relaxation alone.