ASCII Character ψ

Psi /ˈ(p)saɪ, ˈ(p)siː/ (uppercase Ψ, lowercase ψ; Greek: ψι psi [ˈpsi]) is the 23rd letter of the Greek alphabet and is associated with a numeric value of 700. In both Classical and Modern Greek, the letter indicates the combination /ps/ (as in English word "lapse"). For Greek loanwords in Latin and modern languages with Latin alphabets, psi is usually transliterated as "ps". The letter's origin is uncertain. It may or may not derive from the Phoenician alphabet. The classical Greek letter was adopted into the early Cyrillic alphabet as "Ѱ". The letter psi is commonly used in physics to represent wave functions in quantum mechanics, such as in the Schrödinger equation and bra–ket notation. It is also used to represent the (generalized) positional states of a qubit in a quantum computer.