Qubit-parity interference despite unknown interaction phases
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arXiv
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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
| Published: |
2026
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| _version_ | 1866912849805180928 |
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| author | Singh, Kratveer Park, Kimin Švarc, Vojtěch Kovalenko, Artem Pham, Tuan Číp, Ondřej Slodička, Lukáš Filip, Radim |
| author_facet | Singh, Kratveer Park, Kimin Švarc, Vojtěch Kovalenko, Artem Pham, Tuan Číp, Ondřej Slodička, Lukáš Filip, Radim |
| contents | Quantum interference between interacting systems is fundamental to basic science and quantum technology, but it typically requires precise control of the interaction phases of lasers or microwave generators. Can interference be observed if those interaction phases are stable but unknown, usually prohibitive for complex state without active control? Here, we answer this question by experimentally preparing a Schrödinger-cat-like state of an internal qubit and a motional oscillator of a trapped $^{40}$Ca$^{+}$ ion, and its robustness to such uncontrolled phase. By applying alternating red and blue sideband pulses, we enforce a strict qubit-parity correlation and interference inherently insensitive to stable but unknown phases of the driving laser. For this qubit-parity interference, we use a minimal two-pulse interferometric sequence to demonstrate characteristic visibilities of $20\%$ and $40\%$, which approach the theoretical visibility limit, providing a scalable coherence witness without full state tomography for high-dimensional states. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_18499 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Qubit-parity interference despite unknown interaction phases Singh, Kratveer Park, Kimin Švarc, Vojtěch Kovalenko, Artem Pham, Tuan Číp, Ondřej Slodička, Lukáš Filip, Radim Quantum Physics Quantum interference between interacting systems is fundamental to basic science and quantum technology, but it typically requires precise control of the interaction phases of lasers or microwave generators. Can interference be observed if those interaction phases are stable but unknown, usually prohibitive for complex state without active control? Here, we answer this question by experimentally preparing a Schrödinger-cat-like state of an internal qubit and a motional oscillator of a trapped $^{40}$Ca$^{+}$ ion, and its robustness to such uncontrolled phase. By applying alternating red and blue sideband pulses, we enforce a strict qubit-parity correlation and interference inherently insensitive to stable but unknown phases of the driving laser. For this qubit-parity interference, we use a minimal two-pulse interferometric sequence to demonstrate characteristic visibilities of $20\%$ and $40\%$, which approach the theoretical visibility limit, providing a scalable coherence witness without full state tomography for high-dimensional states. |
| title | Qubit-parity interference despite unknown interaction phases |
| topic | Quantum Physics |
| url | https://arxiv.org/abs/2601.18499 |