138 results about "Homodyne detection" patented technology

One aspect of the present invention is related to a quantum cryptographic scheme comprising at least one sending unit including a physical means of encoding and distributing a raw key in the quadrature components of quantum coherent states that are continuously modulated in phase and amplitude, at least one receiving unit containing a physical means of performing homodyne detection of the quantum coherent states in order to measure the quadrature components of the states, a quantum channel for connecting the sending unit to the receiving unit, a two-way authenticated public channel for transmitting non-secret messages between the sending unit and the receiving unit, a quantum key distribution protocol ensuring that the information tapped by a potential eavesdropper can be estimated from the quantum channel parameters, and a direct or reverse reconciliation protocol that converts the raw continuous data into a common binary key.

A quantum noise random number generator system that employs quantum noise from an optical homodyne detection apparatus is disclosed. The system utilizes the quantum noise generated by splitting a laser light signal using a beamsplitter having four ports, one of which receives one of which is receives the laser light signal, one of which is connected to vacuum, and two of which are optically coupled to photodetectors. Processing electronics process the difference signal derived from subtracting the two photodetector signals to create a random number sequence. Because the difference signal associated with the two photodetectors is truly random, the system is a true random number generator.

Feedback loops can be used to shift and stabilize the carrier-envelope phase of a frequency comb from a mode-locked fibers laser or other optical source. Compared to other frequency shifting and stabilization techniques, feedback-based techniques provide a wideband closed-loop servo bandwidth without optical filtering, beam pointing errors, or group velocity dispersion. It also enables phase locking to a stable reference, such as a Ti:Sapphire laser, continuous-wave microwave or optical source, or self-referencing interferometer, e.g., to within 200 mrad rms from DC to 5 MHz. In addition, stabilized frequency combs can be coherently combined with other stable signals, including other stabilized frequency combs, to synthesize optical pulse trains with pulse durations of as little as a single optical cycle. Such a coherent combination can be achieved via orthogonal control, using balanced optical cross-correlation for timing stabilization and balanced homodyne detection for phase stabilization.

A WDM communication system having two optical-frequency comb sources (OFCSs) that are substantially phase-locked to one another, with one of these OFCSs used at a transmitter to produce a WDM communication signal and the other OFCS used at a receiver to produce multiple local-oscillator signals suitable for homodyne detection of the WDM communication signal received from the transmitter. In one embodiment, the transmitter has (i) a first OFCS adapted to generate a first frequency comb and (ii) an optical modulator adapted to use the first frequency comb to generate a WDM communication signal for transmission to the receiver, this WDM signal having at least two beacon lines. The receiver has a second OFCS adapted to produce a second frequency comb such that the second frequency comb has at least two comb lines having the beacon frequencies, the phases of which comb lines are locked to the phases of the beacon lines of the received WDM signal.

The invention belongs to the field of the secret communication, and provides the chaotic signal production method and device based on the uncertainty quantum noise. The method comprises the followingsteps: S1, preparing a chaotic light source, a slave laser and a signal laser; S2, injecting the chaotic light field into the slave laser, observing an output light field of the slave laser through aspectrum analyzer, and regulating the intensity and the polarization state of the chaotic light field injected into the slave laser until the output light field of the slave laser is the chaotic lightfield; S3, enabling the light emitted from the signal laser to be incident to a balance homodyne detection system to produce the quantum noise signal, performing frequency mixing on the signal and the radio frequency signal, injecting into a modulation port of the slave laser after passing through the low-pass filter, modulating the slave laser, thereby enabling the output light field of the slave laser to be the chaotic signal with the uncertainty. The delay feature of the chaotic signal can be inhibited, and the method can be extensively applied to the chaotic signal production field.

In quantum cryptography communication, a sequence of signals in the form of quantum states randomly selected from a plurality of quantum states each having a different phase modulation angle is transmitted from a data transmitting apparatus. In a data receiving apparatus, if the sequence of samples is received, a plurality of bases corresponding to a plurality of different phase modulation angles are randomly selected, and a homodyne detection process is performed using the selected bases. Information indicating the bases used in the homodyne detection process is sent to the transmitting apparatus. In the data transmitting apparatus, depending on the bases used in the receiving apparatus, bit values are assigned to the plurality of different quantum states selected by the transmitting apparatus, and information indicating the assigned bit values is sent to the data receiving apparatus.

The invention relates to a high-speed true random quantum number generating method, in particular to a method for producing random quantum number at high speed based on vacuum state quantum fluctuation. The problem that the production speed of an existing vacuum random quantum number generator is lower is solved. According to the specific scheme, the high-speed true random quantum number generating method mainly comprises the following steps that the translation effect of Gaussian distribution is firstly exerted to a vacuum state in a phase space, amplification of vacuum-state orthogonal amplitude component noise in the phase space is achieved, and the entropy content introduced by quantum noise in a system is increased; the true random bits which can be extracted in data postprocessing are increased; the background light of a homodyne detection system is strengthened, the sensitivity of the detection system to vacuum noise is improved, and a vacuum noise measurement value is amplified, so that the framing amount of vacuum noise statistics, namely sampling quantization bits are remarkably increased. By adopting the method, the vacuum random quantum number generating rate is effectively improved, and a new means is provided for manufacturing of high-speed random quantum number generators.

The invention provides a vacuum squeezed type light field generator, which comprises a single-frequency dual-wavelength laser (1), a mold cleaner (2), an optical parametric amplifier (3), a cavity length locking system (4) and a balance homodyne detection system (5); wherein the mold cleaner (2), the optical parametric amplifier (3), the cavity length locking system (4) and the balance homodyne detection system (5) are arranged on an optical base; and the mold cleaner (2) consists of a first lens (6), a half-wave plate (7), a polarization beam splitter (8), a second lens (9), an optical input head (10), a single-mode polarization maintaining fiber (11) and an optical output head (12) arranged on an optical axis in sequence. The invention has the advantages of compact structure, convenient regulation, high stability and high reliability, and has important application value.

The invention discloses a laser phase generated carrier doppler vibration signal detection system including a signal generation unit, an optical path unit, and a demodulation unit, and the input end of the demodulation unit is connected two orthogonal signals sin (Csin (Omega t) and cos (Csin (Omega t) from the signal generation unit and an interference signal from the optical path unit, so that the demodulation unit can demodulate the vibration signal to be detected. The invention discloses a laser phase generated carrier doppler vibration signal demodulation method. Through the adoption of an orthogonal phase lock +DCM demodulation method, a vibration signal, after being subjected to electro-optical modulation, of a target to be detected is demodulated by multiplication, low-pass filtering, differentiation, subtraction, and integration calculation. According to the invention, the environmental disturbance resistance property of a conventional homodyne detection can be greatly improved at a low cost; and meanwhile, compared with a conventional laser doppler vibration detection method based on acousto-optic frequency shift, the method provided is high in precision, and the system is simple in optical structure and has good environment adaptability.

The invention provides a wavelength division multiplexing OFDM-PON transmission system based on remote difference frequency detection. The system comprises an optical line terminal, a feed-in type optical fiber network, a far-end node, multiple distribution type optical fiber networks and multiple optical network units which are connected in turn. The optical network units are used for processing a downlink OFDM signal and extracting a specific X-polarized optical carrier used for modulating an uplink OFDM signal. Heterodyne detection of the downlink OFDM signal and a downlink local oscillator optical signal is realized by the optical network units, and the uplink OFDM signal is outputted to the far-end node and the optical line terminal via the distribution type optical fiber networks simultaneously. The optical line terminal receives the uplink OFDM signal and performs self-homodyne detection on the uplink OFDM signal. With adoption of an OFDM and WDM reuse mode, effective transmission channels and data transmission rate are increased so that larger transmission capacity is realized. Meanwhile, receiving sensitivity is enhanced by adopting the difference frequency detection technology so that transmission in longer distance is realized.

The invention discloses a continuous variable measurement device-independent quantum key distribution system and an implementation method thereof. The method includes the following steps that: a quantum key transmitting end first transmits a phase reference signal to a quantum key receiving end to replace the local oscillator light; the quantum key receiving end performs homodyne detection on thereceived phase reference signal; according to a measurement result, the quantum key receiving end performs phase compensation on a quantum signal; and then, the quantum key transmitting end and the quantum key receiving end send the quantum signal to a quantum key detection end, a quantum key measurement end performs homodyne detection on the received quantum signal, wherein the local oscillator light required for the homodyne detection is generated locally, and a detection result is sent to the quantum key transmitting end and the quantum key measurement end through a classical channel. According to the scheme of the invention, the security vulnerability that a local oscillator light signal is easily attacked during channel transmission can be solved, and in addition, the detection process can be placed on a third party to prevent attacks against the detector, and thus the actual security of a continuous variable quantum key distribution system can be improved.

Systems and methods for recovering data in a holographic memory system. The systems and methods use homodyne detection to introduce a local oscillator beam into a reconstructed data beam of the recovered hologram. An image of the combined beam comprising the reconstructed data beam and local oscillator beam may be processed to obtain contrast level information for the pixels of the detected image. This contrast level information may then be used to obtain an increased contrast image of the recovered hologram, which may increase the SNR of the recovered data.

A quantum cipher communication system performs communication processing based on quantum cipher. It may have a first communication terminal, a second communication terminal, and a communication path that connects them. The first communication terminal may contain an optical source, a first light-separating device, optical paths, a light-synthesizing device, a second light-separating device, a first phase-modulator, and a homodyne detector that performs homodyne detection based on the reference light separated in the second light-separating device and passed through the first optical path and the signal light separated in the second light-separating device and passed through the second optical path. The second communication terminal may contain a light-sending device, an optical attenuator, a second phase-modulator, and a photon-number-setting device that sets to a predetermined value an average photon number of the signal light sent to the communication path from the light-sending device.

The invention discloses a method for eliminating the carrier channel crosstalk in a self zero difference detection modular division multiplexing system, and belongs to the technical field of communication. According to the method, the influence of coherent beat frequency noise caused by the crosstalk of a signal path of a carrier channel in a few mode optical fiber transmission process by using the method of performing double-sideband modulation on a transmitting end and performing down-conversion restoration on a receiving end by using carrier channel pilot frequency light. By adoption of themethod, the transmission distance of the self zero difference detection modular division multiplexing (MDM-SHD) system is increased without changing the existing few mode optical fiber (FMF) parameter, the requirements of the MDM-SHD system on the mode selection sensitivity of the mode multiplexer /demultiplexer are reduced, meanwhile better BER performance can be guaranteed, and the performanceeffect is good.

The invention provides an all-fiber-pulse balanced homodyne detection apparatus. The all-fiber-pulse balanced homodyne detection apparatus, which is based on a low noise charge sensitive preamplifier, can be used to accurately measure a quadrature component of a weak coherent light field. The apparatus comprises: a 50/50 polarization-maintaining fiber coupler (1), an attenuator (2), a sensor (3), a charge amplifier (4) and a shaping amplifier (5). In the invention, the attenuator is skillfully combined with a tail fiber of the coupler so that negative factors, such as insertion loss, decrease of a degree of polarization and the like, can be avoided. Continuous accurate attenuation of light intensity can be realized. And stability is good. The detection apparatus is all-fiber, possesses a compact structure, a narrow output pulse width, low electronics noise, high quantum efficiency and can run stably for a long time.

An optical SSB-SC modulation section 13 subjects an optical signal fa outputted from an optical source 11 to an optical SSB-SC modulation based on the amplitude of an external electric signal fc to thereby output an optical intensity-modulated signal. An optical phase modulation section 14 subjects the optical signal fa to an optical phase modulation based on the amplitude levels of the first to n^th external electric signals having frequencies f1 to fn to thereby output the resultant signal as an optical phase-modulated signal. An optical combining section 15 combines together the optical intensity-modulated signal and the optical phase-modulated signal. An optical detecting section 16 performs an optical homodyne detection through a squared detection of the optical intensity-modulated signal and the optical phase-modulated signal combined together to thereby produce a wideband modulated signal, being the difference beat signal between the two optical signals. A combining section 17 combines together the wideband modulated signal and the o^th to t^th electric signals having frequencies fo to ft to thereby output the resultant signal as a wideband modulated signal.

The invention discloses a homodyne detection type coherent light transmission system. The homodyne detection type coherent light transmission system comprises a semiconductor laser light source, a first polarized light control device which enables an angle of 45 degrees to be formed between a polarization direction of a laser and an X-axis in an end face of a photoelectric modulator, the photoelectric modulator which modulates same-phase and orthogonal electric signal components to the laser, a second polarization control device which enables an angle of 45 degrees to be formed between the polarization direction of the X-axis light component of a first light beam and a main axis of a first polarizer i and enables an angle of 45 degrees to be formed between a polarization direction of an X-axis light component of a second light beam and a main axis direction of a second polarizer j, a light beam splitter which splits the laser into the first light beam and the second light beam, a quarter-wave plate which enlarges a phase difference between the X-axis component and a Y-axis light component in the first light beam by pi/2, the first/second polarizer which filters away a projection component of the first/second light beam on the main axis of the first/second polarizer i, and a first photoelectric detector, a second photoelectric detector and a baseband signal processing module all of which are used for signal demodulation.

The invention discloses a cross-medium equipment-independent and discrete modulation continuous variable quantum key distribution system. An eight-state quantum state is prepared by a trusted intermediate party through discrete modulation, the eight-state quantum state is sent to Alice and Bob after photon subtraction, Alice and Bob perform demodulation and homodyne detection on the received quantum state respectively, and a security key is established within an effective distance. According to the invention, a continuous variable quantum key distribution technology in a free space is improved, and the quantum state is prepared and sent by the trusted intermediate party, so that the system has equipment independence, and the communication security is ensured; the photon subtraction operation can improve the entanglement degree between the quanta so as to improve the transmission distance; the homodyne detection can effectively filter the interference of the outside on the optical signal, and the detection result can be well obtained even if the optical signal is influenced to a certain extent. The scheme is oriented to equipment independence under an air-water channel, discrete modulation continuous variable quantum key distribution is utilized, and more practicability is brought to free space communication of quanta.

An apparatus includes a first portion operable to convert an optical phase modulation component of a signal being transmitted through a fiber to a RF intensity modulation, the RF intensity modulation comprising a magnitude; and a second portion operable to determine a dispersion of the fiber based on the magnitude of the RF intensity modulation. Optionally, the first portion includes a path-imbalanced interferometer and an optical intensity detector communicating therewith. Optionally, the apparatus further includes a dispersion compensator communicating with the second portion. Optionally, the second portion includes a filter detector or a coherent detector. Optionally, the filter detector includes a bandpass filter and a Schottky diode, and the coherent detector includes a heterodyne detector or a homodyne detector.

An optical homodyne communication system and method in which a side carrier is transmitted along with data bands in an optical data signal, and upon reception, the side carrier is boosted, shifted to the center of the data bands, and its polarization state is matched to the polarization state of the respective data bands to compensate for polarization mode dispersion during transmission. By shifting a boosted side carrier to the center of the data bands, and by simultaneously compensating for the effects of polarization mode dispersion, the provided system and method simulate the advantages of homodyne reception using a local oscillator. The deleterious effects of chromatic dispersion on the data signals within the data bands are also compensated for by applying a corrective function to the data signals which precisely counteracts the effects of chromatic dispersion.