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While Bell inequalities have been violated several times—mostly in photonic systems—their violations within particle physics experiments are less explored. Here, the BESIII Collaboration showcases Bell-violating nonlocal correlations between entangled hyperon pairs.

Untrustworthy sources or detectors mean that quantum entanglement cannot always be ensured, but quantum steering inequalities can verify its presence. Using a highly efficient system, Smithet al. are able to close the detection loophole and clearly demonstrate steering between two parties.

Qubit-cavity entanglement can be used for quantum information processing and for investigating the quantum-to-classical transition with high control. Here, the authors characterize the entanglement between an artificial atom and a cat state and its susceptibility to decoherence through Bell test witnesses.

Researchers demonstrate a reconfigurable integrated quantum photonic circuit. The device comprises a two-qubit entangling gate, several Hadamard-like gates and eight variable phase shifters. The set-up is used to generate entangled states, violate a Bell-type inequality with a continuum of partially entangled states and demonstrate the generation of arbitrary one-qubit mixed states.

A Bayesian game is one in which each player has incomplete information about all other players in the game. Nicolas Brunner and Noah Linden establish a direct connection between Bayesian games and the abstract theory of Bell nonlocality, which has a prominent role in quantum physics.

A high-dimensional hyperentanglement of polarization and energy–time subspaces is demonstrated using a biphoton frequency comb. The long-postulated Hong–Ou–Mandel quantum revival is exhibited, with up to 19 time-bin dimensions and 96.5% visibility.

The BIG Bell Test, which used an online video game with 100,000 participants worldwide to provide random bits to 13 quantum physics experiments, contradicts the Einstein–Podolsky–Rosen worldview of local realism.

A system based on trapped rubidium atoms for generating quantum secure keys between distant users is presented, which could operate in a device-independent fashion.

Heralded entanglement between two independently trapped single rubidium atoms is generated over long telecom fibre links using quantum frequency conversion in an important step towards the realization of large-scale quantum network links.

A photonic anomalous Floquet insulator is emulated in a silicon photonic chip. Up to four-photon topologically protected entangled states are generated in a monolithically integrated emitter in ambient conditions through four-wave mixing on top of the edge modes of the insulator.

Researchers demonstrate that Bell's measure — a commonly used test of quantum nonlocality — can be used in classical optical schemes to separate incoherence associated with statistical fluctuations from incoherence based on correlation. This technique may be useful for quantum information applications such as classical optical coherence theory and optical signal processing.

Physical theories can be classified by the strength of the correlations that they allow to be generated between systems. Here, the authors introduce the set of almost quantum correlations that, despite being larger than strict quantum correlations, do not lead to operational contradictions.

Scalable photonic devices for quantum information processing require on-chip quantum states engineering. Here the authors report the creation of entangled photon pairs on a silicon-on-insulator chip by integrating resonant photon sources, spectral demultiplexers and reconfigurable optics in a single device.

By using qubit recycling, researchers demonstrate a scalable version of Shor's algorithm in which the total number of qubits is one third of that required in the standard protocol. They experimentally implemented a two-photon compiled algorithm to factor N = 21, pointing to larger-scale implementations of Shor's algorithm.

A Bell experiment that is ‘loophole’ free—leaving no room for explanations based on experimental imperfections—reveals a statistically significant conflict with local realism

Starting with wave-particle duality, experiments with light have played a major role in the development of quantum theory. Advances in photonic technologies allow for improved tests of quantum complementarity, delayed-choice and nonlocality.

Erwin Schrödinger introduced in 1935 the concept of ‘steering’, which generalizes the famed Einstein–Podolsky–Rosen paradox. Steering sits in between quantum entanglement and non-locality — that is, entanglement is necessary for steering, but steering can be achieved, as has now been demonstrated experimentally, with states that cannot violate a Bell inequality (and therefore non-locality).

Bell inequalities are a quantitative measure that can distinguish classically determined correlations from stronger quantum correlations, and their measurement provides strong experimental evidence that quantum mechanics provides a complete description. The violation of a Bell inequality is now demonstrated in a solid-state system; the experiment provides further strong evidence that a macroscopic electrical circuit is really a quantum system.

Entanglement is an important resource in quantum-enhanced technologies, but it is difficult to generate, especially in solid-state systems. An experiment now demonstrates the entanglement of two nuclear spins via a parity measurement of the electron spin in a nitrogen-vacancy centre in diamond.

A deterministic violation of the Bell inequality is reported between two superconducting circuits, providing a necessary test for establishing strong enough quantum entanglement to achieve secure quantum communications.

Genetic variation can impact protein complexes and interaction networks, but reconciling genetic and proteomic information remains challenging. To address this need, the authors develop Genoppi —a computational tool for integrating genetics and cell-type-specific proteomics data.

High-dimensional quantum entanglement is generated via a singly filtered biphoton frequency comb, with energy-time entanglement witnessed for both between time bins and frequency bins. Entanglement distribution of such high dimensional entangled state is verified with high quality and provides a testbed for high-dimensional quantum key distribution.

There are good reasons to consider nonlocality to be the defining feature of quantum mechanics, but stronger nonlocal correlations than those predicted by quantum theory could exist, which raises the intriguing question of what lies beyond.

Protein-protein interaction networks of coronary artery disease (CAD) risk genes in human vascular cells are enriched for genetic variants associated with CAD and can be used to guide future research into the molecular pathogenesis of CAD.