Quantum Memory
A device that catches a quantum state, holds it without measuring it, and releases it intact on demand. The quantum analog of RAM, with no backups allowed.
A quantum memory stores a quantum state: catches it, holds it without measuring it (measurement would destroy it), and releases it on demand with its superposition and entanglement intact. It's the quantum analog of RAM, with the added indignity that the no-cloning theorem forbids backups.
Candidates include atomic ensembles, rare-earth ions frozen in crystals, single trapped atoms in cavities, and nitrogen-vacancy centers. The specs in tension are storage time, retrieval efficiency, and fidelity; systems tend to excel at one and disappoint at the others.
Memories matter because they're the pacing item in quantum repeaters and a key enabler for modular quantum computers that pass states between chips.
Boulder's Icarus Quantum plays in this supply chain from the photon side: efficient quantum light sources are the other half of any photon-memory interface.