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 method for quantum key includes providing an initial key in a first data processing device and a second data processing device; providing, in the second data processing device, a quantum signal comprising a plurality of quantum states; determining, in the second data processing device, a plurality of quantum measurement parameters, a raw signal by quantum measuring the plurality of quantum states employing the plurality of quantum measurement parameters; generating with the initial key, in the second data processing device, an encrypted signal; determining, in at least one of the first data processing device and the second data processing device, a reconciled signal from the encrypted signal; determining, in at least one of the first data processing device and the second data processing device, a shared key from the reconciled signal by correcting the first reconciled signal.

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 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 method for quantum key includes providing an initial key in a first data processing device and a second data processing device; providing, in the second data processing device, a quantum signal comprising a plurality of quantum states; determining, in the second data processing device, a plurality of quantum measurement parameters, a raw signal by quantum measuring the plurality of quantum states employing the plurality of quantum measurement parameters; generating with the initial key, in the second data processing device, an encrypted signal; determining, in at least one of the first data processing device and the second data processing device, a reconciled signal from the encrypted signal; determining, in at least one of the first data processing device and the second data processing device, a shared key from the reconciled signal by correcting the first reconciled signal.