Fast quantum operation over multiple quantum bits

Several candidate systems for quantum computing permit direct and efficient implementation of multiqubit gates and hence reduce the number of operations and errors incurred during the execution of a given algorithm. One candidate system relies on Rydberg states, in which a laser excites electrons in neutral atoms to very high energy levels. A paper published in the physical review X journal [1] shows that by collectively following a state with constant energy during the application of a smooth laser pulse, the atoms can implement multiqubit gates with prominent applications in quantum computing and quantum error correction algorithms.

The article uses simple estimates and numerical simulations of the errors estimating acceptable fidelities for gates composed of up to 20 qubits. Remarkably it argues that the central idea of the proposal may also be implemented in other systems, such as superconducting qubits, where similar performances are predicted. The proposal goes beyond the traditional circuit model paradigm of quantum computing, where algorithms are implemented as sequences of one- and two-qubit gates.

The manuscript suggests that now may be a good time to supplement the circuit model paradigm with physically motivated shortcuts to multiqubit gates, for which entire families are already explored within current implementations of quantum computing.

[1] M. Khazali, Klaus Mølmer, “Fast multi-qubit gates via adiabatic evolution in dark state manifolds of Rydberg atoms and superconducting circuits”, Phys. Rev. X 10, 021054 (2020).