dorsal/arxiv
View SchemaOptical coherence and teleportation: Why a laser is a clock, not a quantum channel
| Authors | Howard M. Wiseman |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0303116 |
| URL | https://arxiv.org/abs/quant-ph/0303116 |
| DOI | 10.1117/12.497090 |
| Journal | Proceedings of SPIE Vol. 5111 Fluctuations and Noise in Photonics and Quantum Optics, Eds Derek Abbott, Jeffrey H. Shapiro, Yoshihisa Yamamoto (SPIE, Bellingham, WA, 2003), pp 78-91 |
Abstract
It has been argued [T. Rudolph and B.C. Sanders, Phys. Rev. Lett. {\bf 87}, 077903 (2001)] that continuous-variable quantum teleportation at optical frequencies has not been achieved because the source used (a laser) was not `truly coherent'. Van Enk, and Fuchs [Phys. Rev. Lett, {\bf 88}, 027902 (2002)], while arguing against Rudolph and Sanders, also accept that an `absolute phase' is achievable, even if it has not been achieved yet. I will argue to the contrary that `true coherence' or `absolute phase' is always illusory, as the concept of absolute time on a scale beyond direct human experience is meaningless. All we can ever do is to use an agreed time standard. In this context, a laser beam is fundamentally as good a `clock' as any other. I explain in detail why this claim is true, and defend my argument against various objections. In the process I discuss super-selection rules, quantum channels, and the ultimate limits to the performance of a laser as a clock. For this last topic I use some earlier work by myself [Phys. Rev. A {\bf 60}, 4083 (1999)] and Berry and myself [Phys. Rev. A {\bf 65}, 043803 (2002)] to show that a Heisenberg-limited laser with a mean photon number $\mu$ can synchronize $M$ independent clocks each with a mean-square error of $\sqrt{M}/4\mu$ radians$^2$.
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"abstract": "It has been argued [T. Rudolph and B.C. Sanders, Phys. Rev. Lett. {\\bf 87},\n077903 (2001)] that continuous-variable quantum teleportation at optical\nfrequencies has not been achieved because the source used (a laser) was not\n`truly coherent\u0027. Van Enk, and Fuchs [Phys. Rev. Lett, {\\bf 88}, 027902\n(2002)], while arguing against Rudolph and Sanders, also accept that an\n`absolute phase\u0027 is achievable, even if it has not been achieved yet. I will\nargue to the contrary that `true coherence\u0027 or `absolute phase\u0027 is always\nillusory, as the concept of absolute time on a scale beyond direct human\nexperience is meaningless. All we can ever do is to use an agreed time\nstandard. In this context, a laser beam is fundamentally as good a `clock\u0027 as\nany other. I explain in detail why this claim is true, and defend my argument\nagainst various objections. In the process I discuss super-selection rules,\nquantum channels, and the ultimate limits to the performance of a laser as a\nclock. For this last topic I use some earlier work by myself [Phys. Rev. A {\\bf\n60}, 4083 (1999)] and Berry and myself [Phys. Rev. A {\\bf 65}, 043803 (2002)]\nto show that a Heisenberg-limited laser with a mean photon number $\\mu$ can\nsynchronize $M$ independent clocks each with a mean-square error of\n$\\sqrt{M}/4\\mu$ radians$^2$.",
"arxiv_id": "quant-ph/0303116",
"authors": [
"Howard M. Wiseman"
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"doi": "10.1117/12.497090",
"journal_ref": "Proceedings of SPIE Vol. 5111 Fluctuations and Noise in Photonics\n and Quantum Optics, Eds Derek Abbott, Jeffrey H. Shapiro, Yoshihisa Yamamoto\n (SPIE, Bellingham, WA, 2003), pp 78-91",
"title": "Optical coherence and teleportation: Why a laser is a clock, not a quantum channel",
"url": "https://arxiv.org/abs/quant-ph/0303116"
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