Quantum Bell-triplet states emerge from 151 MeV proton collisions

Researchers from Fudan University in Shanghai, China and the Universidade de Santiago de Compostela in Spain have demonstrated the emergence of a near-pure Bell-triplet state from 151 MeV proton collisions at a 90-degree scattering angle. This work establishes proton-proton scattering as a potential source of high-fidelity entanglement, a key resource for quantum information science typically associated with more controlled systems. Building on this finding, the team proposes a quantum teleportation protocol for proton spins, using the strong interaction’s Hamiltonian for Bell measurement. These results bridge few-body nuclear physics and quantum technology, positioning proton-proton scattering as both an entanglement source and a natural quantum processor. Proton-Proton Scattering Reveals Emergent Bell-Triplet States Proton-proton scattering energy of 151 MeV generates a near-pure Bell-triplet state when observed at a scattering angle of 90 degrees, a finding that establishes a new regime for observing quantum entanglement. This observation deviates from typical entanglement experiments requiring highly controlled systems, instead demonstrating the emergence of this quantum property from relatively high-energy particle collisions. The scattering amplitude itself functions as a transition operator, effectively connecting different Bell states within this specific kinematic regime. Quantifying the entanglement properties of these collisions relies on metrics like entanglement power and concurrence, tools used to assess the average entanglement generated by the scattering process across various initial spin states. Researchers parameterized these initial states using angles defining the spin orientations of the two protons on their respective Bloch spheres, allowing for a detailed analysis of the entanglement generated. This analysis revealed a distinct peak indicating a strongly entangled spin-triplet state, a previously unexplored phenomenon in proton-proton scattering.

The team’s calculations, using chiral effective field theory interactions up to N3LO with incorporated Coulomb effects, further illuminate the characteristics of this emergent entanglement. The observed Bell-triplet state offers a high-quality source for subsequent Bell tests and related applications, potentially extending quantum information protocols into the femtometer scale. The underlying spin amplitude acts as a Bell transition operator, specifically of the form proportional to, effectively mediating the transition between Bell states. Building on this, the researchers propose a novel proton-spin teleportation protocol, using the intrinsic Hamiltonian of the strong interaction to perform the necessary Bell measurement. “The realization of such spin teleportation via the strong interaction would extend the reach of quantum information protocols into the femtometer regime,” the authors write, suggesting a new method for the faithful transfer and manipulation of nuclear quantum states.

The team’s partial-wave decomposition of the Bell-triplet weight, W10, at leading order in chiral EFT, further clarifies the underlying mechanisms driving this entanglement. These calculations, excluding contributions from the 1S0 and 3P0 components, provide a detailed understanding of the spin structure responsible for the observed Bell-triplet state. While entanglement power has been a topic of theoretical interest in nuclear physics, its direct experimental determination has remained a challenge until now. Z. X. Shen, H. Y. Shang and Y. G. Ma of Fudan University, along with Y. Ayyad and C. Filgueira of the Universidade de Santiago de Compostela, contributed to the study. The work builds upon earlier investigations into spin entanglement, referencing a nuclear Bell test that used spin-singlet states generated by low-energy proton-proton scattering. A subsequent Bell test using proton singlet pairs was not realized until 2006, highlighting the technical hurdles overcome in this latest research.

The team’s findings demonstrate that proton-proton scattering at the specified energy and angle produces a near-pure Bell-triplet state, represented as |Ψ+⟩, providing a high-quality triplet source for future quantum applications. This state’s purity is important for effective quantum information processing, as it minimizes errors and maximizes the fidelity of quantum operations. The protocol relies on exploiting the strong interaction’s intrinsic Hamiltonian, offering a unique approach to performing the Bell measurement required for teleportation. The ability to generate and manipulate entanglement within nuclear systems opens new avenues for exploring fundamental quantum phenomena and developing novel quantum technologies.

The team’s detailed analysis of the scattering process and the resulting Bell-triplet state provides a solid foundation for future research in this emerging field.

Spin Amplitude Functions as a Bell Transition Operator By employing entanglement measures as probes, scientists identified this unique kinematic region, establishing a new benchmark for constraining nuclear interactions and enabling Bell-type tests within a nuclear environment. Detailed analysis reveals that the spin amplitude, in the Bell basis, is dominated by a single matrix element, approximately -3. 845-i0., with all other components reduced by more than one order of magnitude. This dominance allows for coherent conversion of an incoming proton pair’s |Φ⁻⟩ component into the Bell triplet |Ψ⁺⟩, effectively acting as a quantum switch for spin states. The implications extend to quantum teleportation, as the researchers propose a protocol for proton spins using this emergent Bell transition operator to perform a Bell measurement effectively. The protocol relies on spatially separating protons and using the scattering process to transfer the spin state of a target proton to a remote proton, up to an inversion of the quantization axis. Quantifying the effectiveness of this transition, the team calculated a similarity metric, S(E,θ), between the physical spin amplitude and the ideal Bell transition operator, revealing a high-similarity “island” around the 151 MeV, 90-degree scattering parameters. This indicates that the nuclear force naturally generates an amplitude closely resembling the desired Bell-state transition over a broad kinematic window, increasing the robustness of the proposed teleportation scheme.

The team’s calculations, detailed in supplemental materials, also address potential limitations such as spin transport, decoherence and the efficiency of receiver-proton spin readout, providing a comprehensive assessment of the protocol’s feasibility. The ability to achieve this transition is not limited to pure states; the proposed protocol can be extended to general mixed states, broadening its applicability to real-world quantum information processing scenarios.

The team details the low-energy singlet-based scheme in supplemental materials, but focuses on the latter for its potential to realize approximately a Bell transition operator, mapping |Φ⁻⟩ into |Ψ⁺⟩. The discovery of this emergent Bell-triplet state and its function as a transition operator positions proton-proton scattering as a promising resource for quantum information processing, bridging the gap between fundamental nuclear physics and cutting-edge quantum technology.

Entanglement Measures Quantify Nuclear Spin Correlation This specific kinematic regime, denoted as (E⊙, θ⊙) demonstrates conditions favorable for strong spin entanglement, a finding that moves beyond the previously understood low-energy enhancements originating from the singlet state. Calculations using the Nijmegen PWA93 database and chiral effective field theory demonstrate the emergence of a nearly pure Bell-triplet state at this energy and angle, regardless of chiral order beyond leading order. The research team’s application of entanglement measures, inspired by quantum information science, provides a new benchmark for constraining nucleon-nucleon interactions and offers a realistic setting for Bell-type tests. Scaling the tensor component of the nuclear potential within the N3LO chiral EFT interaction demonstrates a direct link between the tensor force and the observed entanglement; reducing the tensor strength significantly suppresses the concurrence peak, while restoring it recovers both concurrence and a related entanglement measure, W(10), near (E⊙, θ⊙). This indicates that the tensor operator, S(12) = 3(σ1·r)(σ2·r) – σ1·σ2, actively couples magnetic components and transfers amplitude into the ms = 0 triplet sector, facilitating entanglement generation. However, the tensor contribution alone is insufficient to fully explain the observed effect. Analysis based on the Argonne series of nuclear forces, detailed in supplemental materials shows that a central interaction does not produce the triplet window, a tensor-only extension provides only partial enhancement, and the inclusion of spin-orbit operators is necessary to closely match the realistic case. This suggests a complex interplay of nuclear forces is responsible for the observed entanglement, providing a pathway for precision measurements of spin entanglement to directly constrain the spin-dependent nuclear interaction, particularly its tensor and spin-orbit sectors. In this unique kinematic regime, the scattering amplitude functions as a transition operator connecting distinct Bell states. The study’s approach exemplifies how concepts from quantum information science can offer new perspectives on nucleon-nucleon scattering and the nuclear force, areas long considered well understood. By adopting entanglement measures as quantum-information-inspired probes, the researchers identified this unique kinematic region and its potential for high-fidelity entanglement generation.

The team’s work establishes a clear connection between fundamental nuclear physics and the development of quantum technologies, opening avenues for exploring entanglement generation in previously unexplored energy regimes. Central to the proposed scheme is the dynamical emergence of the Bell transition operator, which facilitates the transfer of quantum information between protons. This emergent resource, combined with the high degree of entanglement achievable at (E⊙, θ⊙), positions proton-proton scattering as both a source of high-fidelity entanglement and a natural processor for quantum information. The study’s findings offer a novel approach to harnessing the strong interaction for quantum applications, potentially bridging the gap between fundamental physics and emerging quantum technologies.

Quantum Teleportation Protocol for Proton Spins via Strong Interaction Proton collisions at 151 MeV, a specific energy level achieved settings have yielded a near-pure Bell-triplet state, a configuration critical for quantum information processing, according to new research. This observation diverges from typical entanglement creation methods, which usually rely on carefully controlled quantum systems, and suggests that entanglement can arise from the dynamics of high-energy particle interactions. Unlike conventional teleportation schemes requiring external two-qubit gates, this approach uses the scattering process itself to realize the necessary quantum operations, potentially simplifying the architecture of future quantum devices. The protocol relies on coincident detection of outgoing protons, which both heralds successful operation and explicitly reflects the probabilistic nature of the process, reducing the typical two-bit message required for standard teleportation to a single bit. The observed enhancement of entanglement occurs at a scattering angle of 90 degrees, a symmetric profile reflecting the indistinguishability of the two protons involved. Two pronounced enhancements were observed, one at low energies, below 10 MeV and another at the identified (151 MeV) kinematic point, denoted as (E⊙, θ⊙). These regions favor strong spin entanglement, with the low-energy enhancement originating from a configuration long recognized as essential for nuclear Bell tests with proton singlet pairs. Consequently, any incoming two-proton state with nonzero overlap with a specific Bell state is coherently converted into a Bell triplet by proton-proton scattering near (E⊙, θ⊙). The behavior at 151 MeV contrasts sharply with the low-energy regime, where the scattering amplitude acts as a Bell-singlet projector. This evolution from projection to transition-operator-like behavior reveals that the nuclear spin amplitude can function as a physically realized spin-entanglement processor, with the strong interaction providing the underlying mechanism for Bell-state manipulation. “By effectively implementing a Bell measurement through this transition mechanism, the pp scattering provides the physical resource required for MeV-scale spin teleportation,” the researchers write. This realization moves beyond the need for explicit gate-level control of individual hadronic spin qubits, a significant challenge in traditional quantum computing architectures.

The team’s work extends quantum teleportation, previously demonstrated in photonic and atomic platforms, into the femtometer/MeV domain, reducing exposure to external environmental noise. This advancement could also provide a pathway to map nuclear states onto accessible platforms, unlocking new avenues for probing nuclear structure via quantum state tomography. While entangled proton pairs can be generated through various methods, including elastic proton-proton scattering and charge-exchange reactions, the current protocol offers a unique advantage by exploiting the intrinsic properties of the strong interaction.

This research establishes a novel approach to quantum information processing, using the strong interaction as a fundamental resource for entanglement generation and manipulation. The ability to perform spin teleportation at the MeV scale opens up new possibilities for exploring quantum phenomena in nuclear systems and potentially developing new quantum technologies. 👉 More information🗞 Spin Teleportation via Bell-Triplet States Emergent from Proton-Proton Scattering✍️ Z. X. Shen, H. Y. Shang, Y. G. Ma, D. Bai, S. M. Wang, Z. C. Xu, Y. Ayyad and C. Filgueira🧠 DOI: http://link.aps.org/doi/10.1103/btxt-28ys More like thisPhysicsSuperconductivity’s left flank explained by nuclear quantum effectsQuantum PhysicsError in quantum state prep drops as evolution gets smootherQuantum Research NewsU of Toronto team spots quantum magnetism with eight poles, not twoQuantum Research NewsQuantum Moire exciton superlattices switch from opaque to transparentStay currentSee today’s quantum computing news on Quantum Zeitgeist for the latest breakthroughs in qubits, hardware, algorithms, and industry deals. Tags: