Quantum Information Processing with Continuous Variables

Quantum information processing with continuous variables (CV) exploits the continuous spectra of bosonic quadrature operators, typically realised in optical or microwave fields, to encode, manipulate and transmit quantum information. Unlike discrete-variable schemes that rely on two-level systems, CV approaches employ Gaussian states—such as squeezed and coherent states—and non-Gaussian resources to achieve deterministic entanglement distribution, high-bandwidth operation and scalable multiplexing in time or frequency domains. Central protocols include measurement-based quantum computation on CV cluster states, quantum teleportation using Gaussian entanglement, and error correction via bosonic codes. Advances in integrated photonic platforms, high-efficiency homodyne detection and fast real-time feedforward have enabled practical demonstrations of universal gate sets, fault tolerance and broadband quantum networks. These developments hold global significance for secure communications, quantum-enhanced metrology and the eventual realisation of large-scale quantum processors.

Research from Nature Portfolio

Recent studies have demonstrated a fast, flexible nonlinear feedforward protocol that harnesses non-Gaussian ancillary states to perform essential measurements for fault-tolerant, measurement-based quantum computation, achieving a significant reduction in excess noise compared with classical ancilla. This advance paves the way for universal CV quantum processors with enhanced noise resilience. Another breakthrough employed orbital angular momentum multiplexed continuous-variable entanglement to realise nine parallel channels of deterministic all-optical quantum teleportation, successfully transmitting superposition-mode coherent states with fidelities surpassing the classical limit. This multiplexing strategy offers a scalable route to high-capacity quantum communication networks.

Quantum Information Processing with Continuous Variables publication trend

The graph below shows the total number of articles in quantum information processing with continuous variables across all publications each year (not limited to Nature Index journals).

Technical terms

Continuous-variable quantum information: A framework using quadrature amplitudes of bosonic modes to encode and process quantum data via continuous spectra.

Gaussian state: A quantum state whose Wigner function is Gaussian, fully specified by mean values and covariance of quadrature operators.

Non-Gaussian operation: An operation that produces non-Gaussian features in the state’s Wigner function, essential for universality and error correction.

Squeezed state: A state in which the variance in one quadrature is reduced below the standard quantum limit at the expense of increased variance in the conjugate quadrature.

Cluster state: A highly entangled multipartite resource state enabling universal measurement-based quantum computation through sequential measurements.

Feedforward: A technique whereby measurement outcomes are used to adjust subsequent operations in real time to steer quantum evolution.

Binomial code: A bosonic error-correcting code formed from superpositions of Fock states with binomial weighting to correct loss, gain and dephasing errors.

References

1. Nonlinear feedforward enabling quantum computation. Nature Communications (2023).
2. Orbital angular momentum multiplexed deterministic all-optical quantum teleportation. Nature Communications (2020).
3. Deterministic all-optical quantum state sharing. Advanced Photonics (2023).
4. New Class of Quantum Error-Correcting Codes for a Bosonic Mode. Physical Review X (2016).
5. High-Threshold Fault-Tolerant Quantum Computation with Analog Quantum Error Correction. Physical Review X (2018).