British Telecommunications Public Limited Company

Amelia Lees

Marco Menchetti

Liam Bussey

Fraser Ashley Burton

Timothy Whitley

This invention provides an electromagnetic field detector, a system comprising the electromagnetic field detector, and a method of operating an electromagnetic field detector, the electromagnetic field detector comprising a first optical signal interface configured to receive, from one or more remote optical sources, a first optical signal; an electromagnetic field transmitter configured to transmit a local oscillator electromagnetic field generated from the first optical signal, the electromagnetic field transmitter comprising: a photocurrent generator configured to generate a photocurrent from the first optical signal; and an antenna interface configured to supply the photocurrent to an antenna to transmit the local oscillator electromagnetic field; a second optical signal interface configured to receive, from the one or more remote optical sources, a probe optical signal and a coupling optical signal; and a transmission medium configured to be excited by the probe optical signal and further excited by the coupling optical signal, wherein the probe optical signal has a probe frequency set to excite electrons of the transmission medium to a first excited state and the coupling optical signal has a coupling frequency set to excite electrons of the transmission medium to a predetermined Rydberg state so as to induce an Electromagnetic Induced Transparency, EIT, effect, wherein the transmission medium is further configured to receive a phase-modulated electromagnetic field from a remote transmitter and the local oscillator electromagnetic field such that the combination of the phase-modulated electromagnetic field and the local oscillator electromagnetic field causes a change in the probe optical signal from which a phase state of the phase-modulated electromagnetic field can be detected.

Electromagnetic field detector

This invention provides a method of detecting a photon in a first frequency range, the method comprising the steps of: exciting a first transmission medium by a first probe signal at a first probe frequency, wherein the first probe signal excites electrons of the first transmission medium from a ground state of the first transmission medium to a first excited state of the first transmission medium; exciting the first transmission medium by a first coupling signal at a first coupling frequency, wherein the first coupling signal overlaps with the first probe signal in the first transmission medium and excites electrons of the first transmission medium to a predetermined excited state of the first transmission medium such that a first photon in the first frequency range and having a first polarisation incident upon the first transmission medium excites an electron in the predetermined excited state of the first transmission medium to a further excited state of the first transmission medium, wherein a first photon in a second frequency range is emitted as part of a subsequent deexcitation of the electron from the further excited state of the first transmission medium; detecting the first photon in the first frequency range and having the first polarisation by detecting the first photon in the second frequency range; exciting a second transmission medium by a second probe signal at a second probe frequency, wherein the second probe signal excites electrons of the second transmission medium from a ground state of the second transmission medium to a first excited state of the second transmission medium; exciting the second transmission medium by a second coupling signal at a second coupling frequency, wherein the second coupling signal overlaps with the second probe signal in the second transmission medium and excites electrons of the second transmission medium to a predetermined excited state of the second transmission medium such that a second photon in the first frequency range incident upon the second transmission medium and having a second polarisation excites an electron in the predetermined excited state of the second transmission medium to a further excited state of the second transmission medium, wherein a second photon in the second frequency range is emitted as part of a subsequent deexcitation of the electron in the further excited state of the second transmission medium; and detecting the second photon in the first frequency range having the second polarisation by detecting the second photon in the second frequency range. This invention also provides a detector and system for implementing said method.

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London, United Kingdom

Amelia Lees