2026-10-16 · arXiv Quantum Physics
arXiv:2607.27144v3 Announce Type: replace
Abstract: Multi-degree-of-freedom photonic quantum processing requires routing between degree-of-freedom (DOF) qubit encodings on a single photon. A SWAP between polarization and time-bin qubits is an advantageous primitive for such architectures, however conventional early/late time-bin encoding does not support bidirectional logical time-bin flips from late to early which limits the ability to implement certain quantum operations. We introduce a parity-based time-bin encoding in which logical $\ket{0}_T$ and $\ket{1}_T$ correspond to even and odd multiples of a spacing $\Delta t$, so that a physical delay of $\Delta t$ implements $\ket{0}_T \leftrightarrow \ket{1}_T$. This encoding is the enabling ingredient that makes a polarization-controlled delay line implement $\mathrm{CNOT}_{P \rightarrow T}$ and aligns naturally with periodic refractive index modulation for $\mathrm{CNOT}_{T \rightarrow P}$. Composing three such CNOT operations sequentially results in a deterministic SWAP between polarization and time-bin degrees of freedom. We quantify how EOM voltage errors reduce the polarization-flip probability and estimate timing requirements from modulator switching, detector resolution, and timing jitter, giving an illustrative timing budget.
原文链接：https://arxiv.org/abs/2607.27144
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