Quantum Coherence in Information Processing Systems

Quantum coherence, the capacity of a system to exist in superposed states, underpins the distinct advantages of quantum information processing over classical schemes. By harnessing coherent superpositions, quantum devices can perform parallel computations, enable secure communication protocols and enhance precision in sensing and metrology. However, the practical realisation of coherent operations faces challenges from environmental coupling and intrinsic noise, which induce decoherence and degrade quantum performance. Contemporary research seeks to protect and exploit coherence through error-correcting codes, reservoir engineering and novel control techniques. This endeavour spans the design of coherent light-matter interfaces, the development of resource-theoretic frameworks to quantify coherence as a consumable resource, and the integration of coherent elements into scalable architectures. The global significance of this field lies in its potential to transform cryptography, materials design and sensor networks, while driving fundamental insights into the boundary between quantum and classical behaviour.

Research from Nature Portfolio

Recent studies have demonstrated the deterministic generation of large-amplitude optical cat states by combining interaction-free measurement with the quantum Zeno effect, allowing fragile microscopic systems to become entangled with strong light fields while preserving coherence. This method operates in a weak-field regime to protect the quantum property of the microscopic subsystem and tolerates moderate photon loss, pointing the way towards high-fidelity non-Gaussian states for quantum communication and metrology. Foundational work on the thermodynamic role of coherence has revealed that conventional free-energy relations are insufficient to describe coherence transformations, leading to a new set of asymmetry constraints that capture the irreversibility of coherence conversion and its contribution to work extraction. Complementary research has clarified the interplay between coherence, quantum discord and deficit in bipartite systems, establishing uncertainty-like relations that link coherence measures to entropic quantities and highlighting coherence as a unifying resource in quantum correlations.

Research from all publishers

Innovative approaches in free-electron–photon interactions have been used to generate optical cat states with pronounced Wigner negativity and squeezing by exploiting multi-path quantum interference; projection measurements on the electron enable non-Gaussian light states with metrological advantages, and oscillatory fidelity peaks reveal pathways to fast state preparation. In the realm of quantum metrology, the relative entropy of coherence has been shown to quantify performance in Bayesian estimation protocols, establishing an equality that relates ensemble coherence to the gap between optimal Holevo information and accessible mutual information, thus offering a direct operational interpretation of coherence measures. Advances in quantum image processing frameworks now employ density-matrix representations to model open quantum systems; three novel schemes for grey-scale and colour images incorporate environmental effects via operator-sum decompositions, enabling robust image evolution under realistic noise channels and paving the way for quantum-enhanced imaging applications.

Quantum Coherence in Information Processing Systems publication trend

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

Technical terms

Quantum coherence: The property of a system to exhibit superposition between basis states, enabling interference phenomena. Decoherence: The process by which interaction with an environment causes loss of coherence and transition to classical mixtures. Resource theory of coherence: A formal framework to quantify, manipulate and interconvert coherence as a resource under restricted operations. Wigner negativity: A signature of non-classicality seen as negative regions in the Wigner function representation of a quantum state. Density matrix: A mathematical operator describing both pure and mixed states, incorporating statistical and quantum uncertainties. Quantum Zeno effect: The inhibition of quantum evolution induced by frequent measurement or interaction that effectively freezes the system’s state.

References

1. Generating optical cat states via quantum interference of multi-path free-electron–photons interactions. Science Bulletin (2023).
2. Relative Entropy of Coherence Quantifies Performance in Bayesian Metrology. PRX Quantum (2024).
3. Quantum image representations based on density matrices in open quantum systems. EPJ Quantum Technology (2024).
4. Method to deterministically generate large-amplitude optical cat states. Communications Physics (2024).
5. Description of quantum coherence in thermodynamic processes requires constraints beyond free energy. Nature Communications (2015).
6. Quantum coherence and correlations in quantum system. Scientific Reports (2015).