Continuous-variable Quantum Computing Mirrors Discrete-variable Systems

Varun Upreti and Ulysse Chabaud of DIENS, École Normale Supérieure, have identified a new property in continuous-variable quantum circuits, termed that mirrors the role of coherence in discrete-variable systems. Their work establishes symplectic coherence as a necessary component for achieving universal computation in continuous-variable quantum computers, alongside non-Gaussianity and entanglement.

The researchers developed a classical simulation algorithm that efficiently tackles computations with low symplectic coherence, revealing its importance as a limit to classical simulation. This discovery demonstrates that the interplay of symplectic coherence, non-Gaussianity and entanglement in continuous-variable quantum computing parallels the discrete-variable relationship between coherence, magic and entanglement via the Gottesman-Kitaev-Preskill encoding.

Non-Gaussianity and Entanglement Enable Universal CV Computation

The absence of symplectic coherence within continuous-variable (CV) permits efficient classical simulation, establishing this property as a fundamental requirement for achieving computational universality in this approach to quantum computing. Researchers demonstrated that circuits lacking symplectic coherence can be efficiently modeled using conventional computers, highlighting its importance as a resource for quantum advantage. This ability to classically simulate circuits with low symplectic coherence is particularly noteworthy because it defines a clear boundary for what can be achieved with existing classical algorithms.