Quantum Coherence and Wave-Particle Duality in Quantum Systems

Quantum coherence and wave-particle duality lie at the heart of quantum mechanics, governing how microscopic systems evolve and how they reveal their nature under observation. Coherence describes the maintenance of fixed-phase relationships between quantum states, enabling superposition and interference. Wave-particle duality expresses the complementary aspects of quantum objects: they can produce diffraction and interference patterns characteristic of waves, yet also be detected as discrete particles. The interplay between coherence and duality has profound implications for foundational studies and for emerging quantum technologies, including computing, sensing and secure communications. Quantitative measures of coherence and duality, such as coherence monotones, fringe visibility and path distinguishability, allow rigorous tests of Bohr’s complementarity principle. Recent advances have extended simple two-path scenarios to multipath interferometry, integrated photonic platforms and hybrid quantum circuits, revealing new trade-off relations and practical routes to preserve coherence in the presence of environmental noise.

Research from Nature Portfolio

Recent studies have demonstrated that single photons can be entangled in their wave-particle degree of freedom, generating nonclassical correlations between two photons’ dual behaviours. By encoding wave and particle states into distinct optical paths and recombining them coherently, researchers have shown deterministic generation of wave-particle entanglement, opening avenues to exploit this degree of freedom for information encoding and quantum communication protocols. Another advancement has generalised delayed-choice experiments to multipath interferometers realised on large-scale silicon photonic chips. In these experiments, coherent superpositions across multiple paths are controlled by quantum-programmable Hadamard operations, and wave versus particle character is tuned by quantum-controlled beam-splitter settings. This work establishes a multipath duality relation, unifying particle predictability and path coherence in high-dimensional systems and benchmarking integrated quantum photonic platforms for complex quantum-state processing.

Quantum Coherence and Wave-Particle Duality in Quantum Systems publication trend

The graph below shows the total number of articles in quantum coherence and wave-particle duality in quantum systems across all publications each year (not limited to Nature Index journals).

Technical terms

Quantum coherence: The property of a quantum system to maintain fixed-phase relationships among basis states, enabling interference effects in superposition.

Wave-particle duality: The principle that quantum entities can exhibit both wave-like interference and particle-like localisation, depending on the measurement context.

Which-path information: Data indicating the route taken by a quantum particle in an interferometer, typically reducing interference visibility when obtained.

Fringe visibility: A quantitative measure of interference contrast, defined by (I_max – I_min)/(I_max + I_min) in an interference pattern.

Entanglement: A nonclassical correlation between quantum systems in which the joint state cannot be factored into independent subsystems, serving as a key resource for quantum information.

References

1. Entanglement of photons in their dual wave-particle nature. Nature Communications (2017).
2. A generalized multipath delayed-choice experiment on a large-scale quantum nanophotonic chip. Nature Communications (2021).
3. Entanglement-interference complementarity and experimental demonstration in a superconducting circuit. npj Quantum Information (2023).
4. Device-independent verification of quantum coherence without quantum control. Cell Reports Physical Science (2023).