dorsal/arxiv
View SchemaAdaptive Phase Measurements
| Authors | Dominic Berry |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0202136 |
| URL | https://arxiv.org/abs/quant-ph/0202136 |
Abstract
In this thesis I consider the general problem of how to make the best possible phase measurements using feedback. Both the optimum input state and optimum feedback are considered for both single-mode dyne measurements and two-mode interferometric measurements. I derive the optimum input states under general dyne measurements when the mean photon number is fixed, both for general states and squeezed states. I propose a new feedback scheme that introduces far less phase uncertainty than mark II feedback, and is very close to the theoretical limit. I also derive results for the phase variance when there is a time delay in the feedback loop, showing that there is a lower limit to the introduced phase variance, and this is approached quite accurately under some conditions. I derive the optimum input states for interferometry, showing that the phase uncertainty scales as 1/N for all the common measures of uncertainty. This is contrasted with the |j0>_z state, which does not scale as 1/N for all measures of phase uncertainty. I introduce an adaptive feedback scheme that is very close to optimum, and can give scaling very close to 1/N for the uncertainty. Lastly I consider the case of continuous measurements, for both the dyne and interferometric cases.
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"abstract": "In this thesis I consider the general problem of how to make the best\npossible phase measurements using feedback. Both the optimum input state and\noptimum feedback are considered for both single-mode dyne measurements and\ntwo-mode interferometric measurements. I derive the optimum input states under\ngeneral dyne measurements when the mean photon number is fixed, both for\ngeneral states and squeezed states. I propose a new feedback scheme that\nintroduces far less phase uncertainty than mark II feedback, and is very close\nto the theoretical limit. I also derive results for the phase variance when\nthere is a time delay in the feedback loop, showing that there is a lower limit\nto the introduced phase variance, and this is approached quite accurately under\nsome conditions. I derive the optimum input states for interferometry, showing\nthat the phase uncertainty scales as 1/N for all the common measures of\nuncertainty. This is contrasted with the |j0\u003e_z state, which does not scale as\n1/N for all measures of phase uncertainty. I introduce an adaptive feedback\nscheme that is very close to optimum, and can give scaling very close to 1/N\nfor the uncertainty. Lastly I consider the case of continuous measurements, for\nboth the dyne and interferometric cases.",
"arxiv_id": "quant-ph/0202136",
"authors": [
"Dominic Berry"
],
"categories": [
"quant-ph"
],
"title": "Adaptive Phase Measurements",
"url": "https://arxiv.org/abs/quant-ph/0202136"
},
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