quantum state

American  

noun

Physics.

1. the condition in which a physical system exists, usually described by a wave function or a set of quantum numbers.

---

quantum state British  

noun

1. physics a state of a system characterized by a set of quantum numbers and represented by an eigenfunction. The energy of each state is precise within the limits imposed by the uncertainty principle but may be changed by applying a field of force. States that have the same energy are called degenerate See also energy level

---

quantum state Scientific  

1. A description in quantum mechanics of a physical system or part of a physical system. Different quantum states for a physical system show discrete differences in the value of the variables used to define the state. For example, the spin of an isolated electron can take on one of only two values; there are no other quantum states available for the electron and no intermediate values, since spin is quantized. The quantum state is sometimes described by a set of quantum numbers that pick out the appropriate values for describing the state.

---

Etymology

Origin of quantum state

First recorded in 1920–25

Example Sentences

Qubits are extremely fragile, and the slightest changes in the environment can disrupt their delicate quantum state.

From Barron's • Jan. 6, 2026

As qubits exist in a delicate environment, error correction is needed to protect the information from noise that would cause qubits to lose their quantum state.

From MarketWatch • Dec. 11, 2025

"Entangled" means the two photons share a single quantum state even when physically apart.

From Science Daily • Nov. 29, 2025

In fact, an idea like the participatory universe that accounts for the role of the observer in determining something’s quantum state could help explain some mathematical conundrums that have appeared in quantum physics, Linde said.

From Salon • Jan. 17, 2025

In particular, no two electrons of the same quantum state can be forced into the same spot.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife