Macroscopic Single-Qubit Operation for Coherent Photons
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arXiv
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| Format: | Preprint |
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2023
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| _version_ | 1866909217754972160 |
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| author | Saito, Shinichi |
| author_facet | Saito, Shinichi |
| contents | Polarisation is described by an $SU(2)$ wavefunction due to macroscopic coherence of photons emitted from a ubiquitous laser source, and thus, a laser pulse is expected to behave as a macroscopic quantum bit (qubit), i.e., a qubit realised by a macroscopic number of photons. Here, we show that an arbitrary single-qubit operation can be carried out for such a macroscopic qubit by employing optical modulators, together with standard optical plates, in a computer-controlled fibre-optic configuration. We named the device as a Poincaré rotator, which allows a dynamic control over a polarisation state by executing an arbitrary amount of rotations on the Poincaré sphere. The Poincaré rotator works as an arbitrary $SU(2)$ operator in a Lie group, by combining a $U(1)$ operation to change the phase and another $U(1)$ operation to change the amplitude of the wavefunction. We have realised various polarisation states, such as $4 \times 4=16$, $8 \times 8=64$, and $10 \times 10=100$ distinguishable states on the sphere. As a locus of the realised polarisation states on the sphere, we have successfully drawn the molecular structure of Buckminsterfullerene (C$_{60}$) and the coastline of the earth. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2304_00013 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Macroscopic Single-Qubit Operation for Coherent Photons Saito, Shinichi Optics Quantum Physics Polarisation is described by an $SU(2)$ wavefunction due to macroscopic coherence of photons emitted from a ubiquitous laser source, and thus, a laser pulse is expected to behave as a macroscopic quantum bit (qubit), i.e., a qubit realised by a macroscopic number of photons. Here, we show that an arbitrary single-qubit operation can be carried out for such a macroscopic qubit by employing optical modulators, together with standard optical plates, in a computer-controlled fibre-optic configuration. We named the device as a Poincaré rotator, which allows a dynamic control over a polarisation state by executing an arbitrary amount of rotations on the Poincaré sphere. The Poincaré rotator works as an arbitrary $SU(2)$ operator in a Lie group, by combining a $U(1)$ operation to change the phase and another $U(1)$ operation to change the amplitude of the wavefunction. We have realised various polarisation states, such as $4 \times 4=16$, $8 \times 8=64$, and $10 \times 10=100$ distinguishable states on the sphere. As a locus of the realised polarisation states on the sphere, we have successfully drawn the molecular structure of Buckminsterfullerene (C$_{60}$) and the coastline of the earth. |
| title | Macroscopic Single-Qubit Operation for Coherent Photons |
| topic | Optics Quantum Physics |
| url | https://arxiv.org/abs/2304.00013 |