Abstract: A system and method for determining a secret crypto-graphic key shared between a sending unit and a receiving unit for secure communication includes obtaining, by the sending unit, a random bit sequence, and transmitting, at the sending unit, a first sequence of electromagnetic pulses to the receiving unit via a communication channel, wherein each electro-magnetic pulse of the first sequence of electromagnetic pulses corresponds to a bit of the random bit sequence according to a ciphering protocol, the signal loss is determined in the communication channel caused by an eavesdropper, and an information advantage is estimated over the eavesdropper based on the determined signal loss. Privacy amplification is performed based on the estimated information advantage in order to establish a shared secret crypto-graphic key.

Abstract: A system and method for determining a secret cryptographic key shared between a sending unit and a receiving unit by using a communication channel comprising spatially separated amplifiers for secure long-distance communication includes transmitting a sequence of electromagnetic pulses via the communication channel through the amplifiers for establishing a shared secret cryptographic key, wherein each electromagnetic pulse corresponds to a bit of a random bit sequence according to a ciphering protocol, and at least one ciphering parameter is determined by maximizing the expected key generation rate using an information theory model, wherein a measured signal loss and at least one amplification parameter are taken into account as input parameters to the information theory model.

Abstract: A system or a method for optical signal amplification includes determining a target operating gain of an optical amplifier; determining a target maximum gain of the optical amplifier; determining an active fiber section length such that the optical signals are amplified with at most the target maximum gain; determining a core cross-sectional area size of the active fiber section based on a maximum allowable pulse shape distortion and a target maximum energy per pulse such that high-energy pulses with the target maximum energy per pulse are distorted by at most the maximum allowable pulse shape distortion; and determining an operating pumping power of the pumping device below the maximum pumping power such that the optical signals are amplified with the target operating gain.

Abstract: A method for quantum key distribution includes determining a ratio between a target maximum gain and a target operating gain of an optical amplifier; determining an active fiber section length such that the optical signals with a target maximum signal power are amplified with at most the target maximum gain; determining an operating pumping power of a pumping device below the maximum pumping power such that the optical signals are amplified with a target operating gain according to the determined ratio between the target maximum gain and the target operating gain; and determining a shared key between a first data processing device and a second data processing device by quantum key distribution comprising amplifying the optical signals via the optical amplifier by operating the pumping device at the operating pumping power.

Abstract: The invention relates to a method for determining the component of a magnetic field in a predetermined direction. The method comprises preparing a quantum system in a coherent superposition state (S1), letting the quantum system evolve for a delay time period (S2) and performing a readout operation and a projective measurement on the quantum system (S3). The steps (S1, S2, S3) are iteratively repeated in an iteration loop, wherein the delay time period increases linearly by the same time increment after each iteration. The method further comprises determining the component of the magnetic field in the predetermined direction according to the outcome of the projective measurements (S4).

Abstract: A system for quantum key distribution includes a first data processing device; a second data processing device; and a transmission line extending between the first data processing device and the second data processing device. The transmission line comprises an inner optical fiber, a shielding layer surrounding the inner optical fiber, and an outer optical fiber surrounding the shielding layer. The first data processing device and the second data processing device are configured to determine a shared key by quantum key distribution via quantum signals along the inner optical fiber. The system is configured to determine outer signal losses along the outer optical fiber.

Abstract: A system and method for quantum key distribution includes determining an intrinsic loss along a quantum channel; generating a pulse sequence; transmitting the pulse sequence via the quantum channel; receiving the pulse sequence; determining invalid signal positions and providing the invalid signal positions; determining a first reconciled signal from the first signal and the invalid signal positions, and determining a second reconciled signal from the second signal and the invalid signal positions; determining a total loss along the quantum channel from the at least one test pulse received, determining a signal loss from the total loss and the intrinsic loss, and providing the signal loss; determining a shared by error correcting the first reconciled signal and the second reconciled signal; and determining an amplified key from the shared key by shortening the shared key by a shortening amount that is determined from the signal loss.

Abstract: A system and method incudes generating a first target cryptocurrency key pair and a corresponding first target cryptocurrency address. A first cryptocurrency asset is transferred from to the first target cryptocurrency address employing a first cryptocurrency protocol, while providing a first password in a first user device and first user data assigned to a first user with a first vault asset corresponding to the at least one first cryptocurrency asset. The first password is transmitted from the first device to the server employing a first quantum key distribution protocol. Upon verification of the first key, a second vault asset is removed from the first user data, and a second target cryptocurrency key pair and a corresponding second target cryptocurrency address of a second cryptocurrency asset corresponding to the second vault asset are transmitted from the server to the first user device employing the first quantum key distribution protocol.

Abstract: The invention relates to a method for determining the component of a magnetic field in a predetermined direction. The method comprises preparing a quantum system in a coherent superposition state (S1), letting the quantum system evolve for a delay time period (S2) and performing a readout operation and a projective measurement on the quantum system (S3). The steps (S1, S2, S3) are iteratively repeated in an iteration loop, wherein the delay time period increases linearly by the same time increment after each iteration. The method further comprises determining the component of the magnetic field in the predetermined direction according to the outcome of the projective measurements (S4).

Abstract: A system and method for determining a secret cryptographic key shared between a sending unit and a receiving unit by using a communication channel comprising spatially separated amplifiers for secure long-distance communication includes transmitting a sequence of electromagnetic pulses via the communication channel through the amplifiers for establishing a shared secret cryptographic key, wherein each electromagnetic pulse corresponds to a bit of a random bit sequence according to a ciphering protocol, and at least one ciphering parameter is determined by maximizing the expected key generation rate using an information theory model, wherein a measured signal loss and at least one amplification parameter are taken into account as input parameters to the information theory model.

Abstract: A system and method for quantum key distribution includes determining an intrinsic loss along a quantum channel; generating a pulse sequence; transmitting the pulse sequence via the quantum channel; receiving the pulse sequence; determining invalid signal positions and providing the invalid signal positions; determining a first reconciled signal from the first signal and the invalid signal positions, and determining a second reconciled signal from the second signal and the invalid signal positions; determining a total loss along the quantum channel from the at least one test pulse received, determining a signal loss from the total loss and the intrinsic loss, and providing the signal loss; determining a shared by error correcting the first reconciled signal and the second reconciled signal; and determining an amplified key from the shared key by shortening the shared key by a shortening amount that is determined from the signal loss.

Abstract: A system and method for determining a secret crypto-graphic key shared between a sending unit and a receiving unit for secure communication includes obtaining, by the sending unit, a random bit sequence, and transmitting, at the sending unit, a first sequence of electromagnetic pulses to the receiving unit via a communication channel, wherein each electro-magnetic pulse of the first sequence of electromagnetic pulses corresponds to a bit of the random bit sequence according to a ciphering protocol, the signal loss is determined in the communication channel caused by an eavesdropper, and an information advantage is estimated over the eavesdropper based on the determined signal loss. Privacy amplification is performed based on the estimated information advantage in order to establish a shared secret crypto-graphic key.

Abstract: The invention relates to a method for determining the component of a magnetic field in a predetermined direction. The method comprises preparing a quantum system in a coherent superposition state (S1), letting the quantum system evolve for a delay time period (S2) and performing a readout operation and a projective measurement on the quantum system (S3). The steps (S1, S2, S3) are iteratively repeated in an iteration loop, wherein the delay time period increases linearly by the same time increment after each iteration. The method further comprises determining the component of the magnetic field in the predetermined direction according to the outcome of the projective measurements (S4).