Quantum Algorithms Database
Quantum Random Access Memory (QRAM)
A proposed architecture for accessing classical data in superposition, theoretically required to realize many quantum machine learning speedups in practice.
Year
2008 (Giovannetti, Lloyd & Maccone)
Inventor(s)
Giovannetti, Lloyd & Maccone
Speedup Type
Exponential Speedup
Difficulty
★★★★★
The Problem
Efficiently loading classical data into a quantum computer so multiple data points can be queried simultaneously in superposition.
How It Works
Proposes a tree-like addressing structure for retrieving memory cells in superposition, requiring specialized quantum hardware distinct from a standard quantum processor's qubits.
Real-World Impact
Widely discussed as the 'input problem' bottleneck — many proposed quantum ML and linear algebra speedups assume QRAM exists, but building an efficient, large-scale QRAM remains a major open hardware challenge.