US5339182A
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Method and apparatus for quantum communication employing nonclassical correlations of quadrature-phase amplitudes
Assignee: California Institute of Technology
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Filing: 1993-02-19
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Granted: 1994-08-16
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Expires: 2013-02-19
Abstract
Abstract An optical information transmission system capable of achieving an information transmission at a signal to noise ratio greater than that which is achievable using classical optical transmission techniques if disclosed. The higher signal to noise ratio is achieved by employing a non-classical, i.e. quantum mechanical, optical transmission technique. To achieve non-classical transmission effects, a non-degenerate optical parametric amplifier is employed to generate a pair of signal beams having highly correlated quantum noise. Information is then encoded within each of the signal beams at a signal level far below the level of the quantum noise. Accordingly, information encoded on the beams is substantially obscured by the quantum noise, thereby effectively preventing unwanted eavesdropping of the transmitted information. After transmission, the pair of separate signal beams are detected and combined by a receiver. The highly correlated quantum noise is eliminated from the signals, leaving substantially only the encoded information. A resulting information signal has a minimum noise level below that which can be achieved using non-classical techniques.
Inventors
- 👤 Harry J. Kimble
- 👤 Zhe-Yu Ou
- 👤 Silvania E. Pereira
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 22:48
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/29; H04B10/291
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
52 words
A method for transmitting information, comprising the steps of: generating a pair of beams having an information signal obscured within correlated quantum noise; transmitting said pair of beams; detecting said pair of beams; and combining said pair of detected beams to subtract said correlated quantum noise and to extract said information signal.
Claim 2
Independent Claim
52 words
A method for transmitting information, comprising the steps of: generating a pair of beams having an information signal obscured within correlated quantum noise; transmitting said pair of beams; detecting said pair of beams; and combining said pair of detected beams to subtract said correlated quantum noise and to extract said information signal.
Claim 3
Dependent Claim
42 words
The method of claim 1, wherein said information signal on said beams has a signal to noise ratio less than 1, and wherein said detected beams are combined to leave an information signal having a signal to noise ratio greater than 1.
Claim 4
Independent Claim
59 words
A method for transmitting information, comprising the steps of: generating first and second optical beams having correlated quantum noise; modulating said first and second optical beams with an information signal transmitting said first and second beams; detecting said first and second beams; and combining said first and second beams to substantially eliminate said correlated quantum noise from said beams.
Claim 5
Independent Claim
59 words
A method for transmitting information, comprising the steps of: generating first and second optical beams having correlated quantum noise; modulating said first and second optical beams with an information signal transmitting said first and second beams; detecting said first and second beams; and combining said first and second beams to substantially eliminate said correlated quantum noise from said beams.
Claim 6
Dependent Claim
44 words
The method of claim 3, wherein said information signal is modulated onto said beams with a signal to noise ratios less than 1, and wherein said detected optical beams are combined to extract information signal having a signal to noise ratio greater than 1.
Claim 7
Independent Claim
79 words
A method for transmitting information, comprising the steps of: generating a plurality of optical beams within a non-degenerate optical parametric amplifier with said optical beams having correlated quantum noise components; modulating an information signal onto said beams with a signal to noise ratio substantially less than 1; transmitting said beams; detecting said beams; and combining said beams to subtract said correlated quantum noise components to extract said information signal with a signal to noise ratio substantially greater than 1.
Claim 8
Independent Claim
79 words
A method for transmitting information, comprising the steps of: generating a plurality of optical beams within a non-degenerate optical parametric amplifier with said optical beams having correlated quantum noise components; modulating an information signal onto said beams with a signal to noise ratio substantially less than 1; transmitting said beams; detecting said beams; and combining said beams to subtract said correlated quantum noise components to extract said information signal with a signal to noise ratio substantially greater than 1.
Claim 9
Independent Claim
68 words
An apparatus for transmitting information, comprising: non-degenerate optical parametric amplification means for generating first and second correlated optical beams, said first and second correlated beams having correlated quantum noise components; means for modulating an information signal onto said beams; means for detecting said first and second beams; and means for combining said first and second beams to eliminate said correlated quantum noise components and extract said information signal.
Claim 10
Independent Claim
68 words
An apparatus for transmitting information, comprising: non-degenerate optical parametric amplification means for generating first and second correlated optical beams, said first and second correlated beams having correlated quantum noise components; means for modulating an information signal onto said beams; means for detecting said first and second beams; and means for combining said first and second beams to eliminate said correlated quantum noise components and extract said information signal.
Claim 11
Dependent Claim
15 words
The apparatus of claim 6, wherein said means for detecting comprises a quadrature phase detector.
Claim 12
Dependent Claim
57 words
The apparatus of claim 6, wherein said means for modulating said information signal on said beams modulates said information signal to produce a signal to noise ratio less than 1, and wherein said means for combining said detected optical beams combines said beams to extract an information signal having a signal to noise ratio greater than 1.
Claim 13
Independent Claim
104 words
A method for transmitting information, comprising the steps of: generating first and second optical beams having correlated quantum noise; generating a third optical beam having an information content; combining said third optical beam with each of said first and second optical beams to produce first and second combined beams, wherein the information content of said third beam is obscured within correlated quantum noise within each individual combined beam; transmitting said first and second combined beams; detecting said first and second combined beams; and combining said first and second combined beams to substantially eliminate said correlated quantum noise from said beams, leaving said information beam.
Claim 14
Independent Claim
104 words
A method for transmitting information, comprising the steps of: generating first and second optical beams having correlated quantum noise; generating a third optical beam having an information content; combining said third optical beam with each of said first and second optical beams to produce first and second combined beams, wherein the information content of said third beam is obscured within correlated quantum noise within each individual combined beam; transmitting said first and second combined beams; detecting said first and second combined beams; and combining said first and second combined beams to substantially eliminate said correlated quantum noise from said beams, leaving said information beam.
Claim 15
Dependent Claim
18 words
The method of claim 9, wherein said first and second beams are generated using a non-degenerate parametric amplifier.
Claim 16
Dependent Claim
14 words
The method of claim 9, wherein said first and second beams have orthogonal modes.
Claim 17
Dependent Claim
30 words
The method of claim 10, wherein said third optical beam is polarized to an angle of 45 degrees from the orthogonal modes of both of said first and second beams.
Claim 18
Dependent Claim
18 words
The method of claim 12, further including the step of spatially separating said first and second combined beams.
Claim 19
Dependent Claim
33 words
The method of claim 13, wherein said step of spatially separating said first and second combined beams includes the step of passing said first and second combined beams through a polarized beam splitter.
Claim 20
Independent Claim
113 words
An apparatus for transmitting information, comprising: means for generating first and second optical beams having correlated quantum noise; means for generating a third optical beam having an information content; means for combining said third optical beam with each of said first and second optical beams to produce first and second combined beams, wherein the information content of said third beam is obscured within correlated quantum noise within each individual combined beam; means for transmitting said first and second combined beams; means for detecting said first and second combined beams; and means for combining said first and second combined beams to substantially eliminate said correlated quantum noise from said beams, leaving said information beam.
Claim 21
Independent Claim
113 words
An apparatus for transmitting information, comprising: means for generating first and second optical beams having correlated quantum noise; means for generating a third optical beam having an information content; means for combining said third optical beam with each of said first and second optical beams to produce first and second combined beams, wherein the information content of said third beam is obscured within correlated quantum noise within each individual combined beam; means for transmitting said first and second combined beams; means for detecting said first and second combined beams; and means for combining said first and second combined beams to substantially eliminate said correlated quantum noise from said beams, leaving said information beam.
Claim 22
Dependent Claim
20 words
The apparatus of claim 15, wherein said means for generating said first and second beams is a non-degenerate parametric amplifier.
Claim 23
Dependent Claim
14 words
The apparatus of claim 15, wherein said first and second beams have orthogonal modes.
Claim 24
Dependent Claim
30 words
The apparatus of claim 17, wherein said third optical beam is polarized to an angle of 45 degrees from the orthogonal modes of both of said first and second beams.
Claim 25
Dependent Claim
17 words
The apparatus of claim 18, further including means for spatially separating said first and second combined beams.
Claim 26
Dependent Claim
22 words
The apparatus of claim 19, wherein said means for spatially separating said first and second combined beams includes a polarized beam splitter.
Claim 27
Dependent Claim
35 words
The apparatus of claim 15, wherein said means for detecting said first and second combined signals comprises a photo detector generating first and second electrical signals representative of the first and second combined optical signals.
Claim 28
Dependent Claim
26 words
The apparatus of claim 21, wherein said means for combining said first and second combined signals comprises means for combining said first and second electrical signals.
References Cited (Backward Citations)
US5113524A
Cited
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