quant-ph

Quantum-information diagnostics of cosmological perturbations with nontrivial sound speed in inflation

Photon Sorting with a Quantum Emitter

This paper demonstrates a passive, on-chip photon-sorting circuit utilizing a solid-state quantum emitter to achieve non-linear photon-photon interactions that enable Bell state measurements with a success probability exceeding the fundamental 50% limit of linear optics.

Symplectic split-operator method for the time-dependent unitary Tavis-Cummings model

This paper presents a fast, memory-efficient, and unitarity-preserving numerical method for simulating the time-dependent Tavis-Cummings model beyond the rotating-wave approximation by transforming the Hamiltonian into a tri-diagonal form via basis permutation, achieving linear computational complexity in both time and memory.

Partial oracles quantum algorithm framework -- Part I: Analysis of in-place operations

This paper presents a construction method for the search iteration operator in the partial oracles quantum algorithm framework by introducing a reciprocal transform with a chain rule for in-place operations and demonstrating its application to SHA-256 components via the new QFrame Python library, while noting that full quantum advantage requires future extension to out-of-place operations.

Variance Geometry of Exact Pauli-Detecting Codes: Continuous Landscapes Beyond Stabilizers

This paper reveals that exact Pauli-detecting quantum codes form connected continuous families characterized by a scalar variance parameter $\lambda^*$, demonstrating that stabilizer codes constitute only measure-zero discrete subsets within a largely unexplored continuum of nonadditive solutions.

The clock ambiguity is back with a vengeance

This paper refutes the claim that non-interacting clocks eliminate the Page-Wootters clock ambiguity by demonstrating that the original proof relies on a mathematical error and that the ambiguity actually extends to both system histories and Hamiltonians, thereby necessitating the physical interpretation of operators to resolve the issue.

Robust continuous symmetry breaking and multiversality in the chiral Dicke model

This paper introduces the chiral Dicke model, a generalized light-matter system with inherent continuous $U(1)$ symmetry, and demonstrates that it exhibits robust symmetry-breaking superradiant phases and a unique "multiversality" phenomenon where distinct universality classes govern the same phase transition depending on the parameter path.

Unitary Time Evolution and Vacuum for a Quantum Stable Ghost

This paper demonstrates that a quantum system comprising a harmonic oscillator polynomially coupled to a ghost with negative kinetic energy can be consistently quantized with a well-defined vacuum and manifestly unitary evolution, provided the system possesses an integral of motion with a positive discrete spectrum that ensures stability despite the Hamiltonian's unbounded spectrum.

Deterministic generation of grid states with programmable nonlinear bosonic circuits

This paper proposes deterministic protocols using programmable nonlinear bosonic circuits to generate a new class of scalable, near-optimal bosonic quantum error-correcting states called "phased-comb states," which offer a viable alternative to standard GKP encodings by naturally arising from circuit symmetries and supporting universal gate operations.

Odd Physics Off the Diagonal: Constraining CP-violating SMEFT with Quantum Tomography

This paper proposes a novel approach using quantum tomography to reconstruct the spin density matrix of diboson systems, enabling the simultaneous and superior constraint of both CP-even and CP-violating SMEFT operators by exploiting full Beyond-Standard-Model signatures, including pure quadratic new physics terms that are typically degenerate in traditional polarisation-blind observables.