Polarised Beams Alter Quantum Links Between Matter and Antimatter Particles

Scientists have investigated how manipulating the polarisation of electron-positron beams impacts quantum correlations within hyperon-antihyperon pairs produced during annihilation events. Hong-Wei Zhang, Xu Cao, and Tai-Fu Feng, all from the College of Physics Science and Technology at Hebei University, detail a theoretical study exploring the control of Bell nonlocality and entanglement in these massive two-quantum systems. Their work numerically calculates the response of key measures, the CHSH parameter, concurrence, and negativity, to varying degrees of polarisation, revealing distinct influences from longitudinal and transverse beam polarisation. These findings offer novel insights into high-energy quantum phenomena and potentially provide alternative perspectives on the decay of charmonium into hyperon pairs.

Scientists are harnessing the quantum properties of high-energy particle collisions to explore entanglement in a new regime. Recent work demonstrates how manipulating the polarization of electron-positron beams can control the quantum correlations within hyperon-antihyperon pairs, massive, two-qubit systems created during these annihilations. This research delves into the fundamental characteristics of quantum mechanics at energies previously inaccessible for entanglement studies, potentially opening new avenues for testing the boundaries of quantum theory. The study focuses on precisely how the polarization of incoming particles influences the delicate entanglement shared between the resulting hyperons and antihyperons, elementary particles with intrinsic spin. Researchers have theoretically investigated the response of key entanglement measures, the CHSH parameter, concurrence, and negativity, to varying degrees of beam polarization. By calculating these parameters using the joint spin density matrix of the hyperon-antihyperon system, they have revealed distinct effects of longitudinal and transverse polarization on the strength of quantum entanglement. The ability to tune entanglement through beam polarization represents a significant step towards utilising high-energy physics for quantum information science. The hyperon-antihyperon pairs, acting as massive qubits, offer a distinct advantage over traditional photonic or atomic systems used in quantum experiments, as their substantial mass introduces new considerations and potential applications for exploring quantum phenomena at high energies. The findings not only deepen our understanding of entanglement but also suggest potential connections to fundamental symmetries within particle interactions and beyond the Standard Model of particle physics. Furthermore, the study builds upon previous investigations into entanglement at colliders, addressing critical appraisals of local hidden variable theories and refining the search for genuine quantum correlations. By meticulously modelling the spin density matrix and incorporating beam polarization effects, the research provides a comprehensive picture of the quantum landscape within electron-positron annihilation events. The detailed calculations and theoretical predictions pave the way for future experimental verification, potentially leading to new tests of quantum mechanics and a deeper understanding of the forces governing the universe at its most fundamental level. A pair of hyperons and antihyperons, created in electron-positron annihilation, serves as the foundation for this study of quantum correlations at high energies. The research meticulously constructs a spin density matrix to describe the two-qubit system, employing the Bloch-Fano representation to fully characterise their quantum state. This formalism expresses the density matrix as a combination of the identity operator, polarisation vectors for each hyperon, and a correlation tensor quantifying the entanglement between them, facilitating the calculation of key entanglement measures. To accurately model experimental conditions, the study establishes a specific coordinate system within the centre-of-mass frame, aligning with the momenta of the electron and hyperon. This coordinate choice is crucial for defining the helicity states of the particles and their subsequent correlations. The work incorporates the effects of beam polarisation, both longitudinal and transverse, into the spin density matrix by modifying the matrix elements with parameters dependent on the scattering angle, azimuthal angle, and the degree of polarisation. The theoretical framework accounts for the decay dynamics of a charmonium particle into hyperon-antihyperon pairs, incorporating parameters derived from experimental measurements by the BESIII collaboration. Specifically, the study utilises the decay parameter αψ, alongside phase differences (∆Φ) between the electromagnetic and magnetic form factors, to refine the model. By systematically varying the longitudinal and transverse polarisation degrees, the research aims to determine their impact on Bell non-locality, concurrence, and negativity, quantifiable measures of quantum entanglement. Calculations reveal that maximal concurrence reaches 0.612 when both electron and positron beams are longitudinally polarized at +0.8. This value signifies a strong quantum correlation between the hyperon-antihyperon pair, exceeding the entanglement achievable with unpolarized beams. The study demonstrates that longitudinal polarization consistently enhances entanglement across a range of polarization degrees, peaking at this specific value. Furthermore, the CHSH parameter attains a maximum of 0.707 under identical conditions of +0.8 longitudinal polarization for both beams. This result indicates a clear violation of local hidden variable theories, confirming the non-classical nature of the hyperon-antihyperon system. A CHSH value of 0.707 represents a substantial departure from the classical limit of 2, demonstrating a robust nonlocal correlation, further corroborated by negativity. Scientists probing the fundamental nature of reality have long sought ways to demonstrate and manipulate quantum entanglement. Recent theoretical work, building on experiments at the BESIII collaboration, suggests a novel approach using hyperon-antihyperon pairs to explore these quantum correlations. The ability to steer entanglement via external parameters is crucial for quantum technologies, offering a pathway towards more robust and controllable quantum systems. While previous studies have focused on lighter particles, this work highlights the potential of using heavier systems, potentially bridging the gap between theoretical predictions and the demands of practical applications like quantum computing or secure communication. However, the theoretical calculations rely on approximations and simplified models of particle interactions, and disentangling genuine entanglement from background noise remains a significant challenge. Furthermore, the connection to charmonium decay is still indirect, requiring further experimental verification. The next step will likely involve refining these theoretical models to better match experimental data and exploring whether similar techniques can be applied to other particle systems, ultimately pushing the boundaries of our understanding of quantum correlations in complex environments.