Quantum instruction set implemented on a superconducting quantum processor

A quantum algorithm consists of a sequence of operations and measurements applied to a quantum processor. To date, the instruction set which defines this sequence has been provided by a classical computer and passed via control hardware to the quantum processor.

A team of researchers at MIT has demonstrated the first experimental realization of a quantum instruction set, in which a fixed sequence of classically-defined gates perform an operation that is fully determined only by a quantum input to the fixed sequence.

Specifically, they have implemented the density matrix exponentiation algorithm, which consumes N copies of the instruction state ρ to approximate the operation e−iρθ (θ an arbitrary angle). Their implementation relies on a 99.7% fidelity controlled-phase gate between two superconducting transmon qubits. The team has achieved an average algorithmic fidelity ≈0.9, independent of the setting of ρ, to circuit depth nearly 90.

This new paradigm for quantum instructions has applications to resource-efficient protocols for validating entanglement spectra, principal component analysis of large quantum states, and universal quantum emulation.

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