Abstract: A system and method for authenticating an optical fiber key includes selecting a plurality of at least partially randomized challenge pulse parameters, generating a first optical challenge pulse based on the plurality of at least partially randomized challenge pulse parameters, determining an optical response signal based on a reflected signal of the first optical challenge pulse from the optical fiber key, applying a comparing algorithm the optical response signal and an expected response based on previously recorded optical response signals of the optical fiber key to a reference optical challenge pulse for determining a similarity metric, and authenticating the optical fiber key based on the similarity metric.

Abstract: A high-temperature superconducting qubit implements a quantum mechanical two-level system. The high-temperature superconducting qubit comprises a first superconductor, a second superconductor, and an overlap region. The first superconductor comprises a first high-temperature superconductor material. The second superconductor comprises a second high-temperature superconductor material. In the overlap region, at least a first section of the first surface and at least a second section of the second surface overlap, the first section and the second section are arranged in parallel at a distance corresponding to a predefined distance, and the first orientation and the second orientation are arranged with an angle corresponding to a predefined angle. The high-temperature superconducting qubit comprises a Josephson junction between the first high-temperature superconductor material and the second high-temperature superconductor material.

Abstract: A quantum key distribution device comprises an input signal path receiving a plurality of optical input signals from a transmitter device, an output signal path connected to the input signal path at a first end and emitting a plurality of first optical output signals at a second end, and a detector signal path connected to the input signal path at a third end and comprising a photon detector device at a fourth end opposite to the third end. The photon detector detects optical input signals from the transmitter device, and the quantum key distribution device establishes a shared quantum cryptographic key with the transmitter device based on the detected optical input signals. The input signal path forms an input path of a Mach-Zehnder interferometer, and the output signal path and the detector signal path form output paths of the Mach-Zehnder interferometer.

Abstract: A ferroelectric nanoparticle capacitor-device comprises a pair of conductive elements electrically insulated from each other, and ferroelectric nanoparticles arranged between the conductive elements of the pair. The ferroelectric nanoparticles are adapted to provide at least three polarization states with different total ferroelectric polarizations.

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 computer-implemented method for providing content of a content author for authentication includes obtaining, by the content author, a first author fragment of content; generating a first state author vector from the first author fragment of content; and creating a first block of key information based on the first author fragment of content, wherein the first block of key information comprises information of the first state author vector and a first digital signature.

Abstract: A method and system for encrypted messaging includes first and second client devices and a quantum key device having a quantum random number generator. The generator provides a first quantum random signal, and the key device provides a symmetric first master key from the first quantum random signal. The master key is transmitted to the first client device and stored. The key device uses the master key to generate an encrypted package by encrypting one of a plurality of keys. The key device generates a second encrypted package. The first pairing key is provided to the first client device by decrypting the first encrypted package using the first master key and providing the first pairing key in the second client device by decrypting the second encrypted package using the second master key to establish an encrypted connection between the first and second client devices.

Abstract: A method for labeling an input vector of features with an output label using a variational quantum circuit given a labeling task includes separating the input vector of features into a plurality of sub-vectors of input data, initializing a plurality of computation qubits in an initial state, and subjecting the plurality of computation qubits to a plurality of layers of quantum gates, wherein each layer of the plurality of layers of quantum gates comprises an entangling gate a plurality of encoding gates for encoding the features of one of the sub-vectors into the computation qubits, and a plurality of variational gates, wherein the sub-vectors of input data for two different layers of quantum gates are different, and wherein variational parameters associated with the variational gates are optimized for predicting an optimal output label for the input vector of features in view of the labeling task according to a training algorithm.

Abstract: A method for driving a quantum computational network for determining an extremal value of a cost function for solutions of a quadratic unconstrained binary optimization problem includes initializing qubits, sequentially applying layers of quantum gates to the qubits, determining an output state of the quantum computational network for obtaining a solution associated with the set of variational parameters {right arrow over (?)}, and determining an output state for shifted variational parameters {right arrow over (?)}* to evaluate a partial derivative with respect to the subset of the variational parameters {right arrow over (?)} for determining a gradient of the cost function based on the output state for the shifted variational parameters {right arrow over (?)}*, and by updating the variational parameters {right arrow over (?)} based on an update function of a moving average over the gradient of the cost function and of a moving average over the squared gradient of the cost function.

Abstract: A computer-implemented method for simulating fluid flow includes solving a Lattice Boltzmann equation for a distribution function, wherein the distribution function is represented in a tensor-train format, and/or all operations carried out for computing the distribution function are carried out with the distribution function in the tensor-train format, the distribution function and/or the tensor train format comprising at least one tensor train, the tensor train having at least one tensor train core.

Abstract: A superconducting qubit circuit and a method of forming a superconducting qubit include superconducting qubit, wherein the superconducting qubit comprises a tunnel junction in a superconducting material having a critical temperature above 1.2 K. The tunnel junction is formed by a disorder-induced tunnel barrier, wherein the disorder is created by spatial crystallographic defects in the superconducting material.

Abstract: A method for quantum key distribution includes generating an encoder initial bit sequence; generating a quantum signal comprising optical pulses by modulating an intensity profile of the optical pulses according to an intensity function depending on a time and on a first encoder value of at least one first bit of the encoder initial bit sequence, and/or modulating a phase profile of the optical pulse according to a phase function which depends on a time and a second encoder value of at least one second bit of the encoder initial bit sequence; transmitting the plurality of optical pulses to a receiver device via a quantum channel; and determining a shared key shared between the transmitter device and the receiver device from the encoder initial bit sequence by classical post-processing and at least one of transmitting classical information to the receiver device and receiving further classical information from the receiver device.

Abstract: A waveguide device comprises a substrate comprising an electro-optical material; a waveguide formed in the electro-optical material; and a plurality of electrodes formed in a vicinity of the waveguide. The electro-optical material has a first refractive index. The waveguide comprises a plurality of tracks. The tracks comprise a second refractive index smaller than the first refractive index, are parallel to each other with a common direction defining a direction of the waveguide, and form an arrangement in a plane perpendicular to the direction of the waveguide. The arrangement comprises at least 40 equilateral triangles of identical side lengths, wherein all three corners of each of the equilateral triangles each coincide with a different track of the plurality of tracks in the plane perpendicular to the direction of the waveguide.

Abstract: A field effect transistor has a negative capacitance gate structure. The field effect transistor comprises a channel and a gate dielectric arranged over the channel. The negative capacitance gate structure comprises a bottom electrode structure comprising a bottom electrode, a multi-domain structure, and a top electrode structure. The multi-domain structure comprises a multi-domain element arranged over the bottom electrode, the multi-domain element comprising a plurality of topological domains and at least one topological domain wall. The top electrode structure comprises a top electrode arranged over the multi-domain element. At least a section of the bottom electrode structure of the negative capacitance gate structure is arranged over the gate dielectric and adapted to be coupled to the channel through the gate dielectric.

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 varistor device for voltage-surge-protecting an electronic circuit at a cryogenic temperature comprises an electric lead composed of a superinsulator material, and electrical contact elements. The electrical contact elements are for connecting different positions along the electric lead to the electronic circuit. The electrical contact elements are in electric contact with the electric lead at the different positions along the electric lead. The electric lead is adapted to provide a superinsulating state or a cooper-pair insulating state at the cryogenic temperature, and to provide a non-linear resistance between the different positions at the cryogenic temperature.

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: An electronics device comprises a substrate, a first layer of a first layered material arranged over the substrate, a second layer of a second layered material arranged over the substrate, an overlap region, and a contact layer. In the overlap region, the second layer is arranged over the first layer, and a section of a bottom surface of the second layer is parallel to a section of a top surface of the first layer. The contact layer comprises a plurality of electrically conductive lines and an electrical insulation element. The plurality of electrically conductive lines comprises a first electrically conductive line and a second electrically conductive line. The first electrically conductive line and/or the second electrically conductive line comprises a superconductor material.

Abstract: A method for determining a preimage element of a cryptographic hash function includes providing an output value of a cryptographic hash function and hash function operations of the cryptographic hash function; for each of the hash function operations, determining at least one hash function relation, comprising an equation and/or an inequality; determining an optimization problem comprising: the output value, at least one constraint assigned to an iteration of the cryptographic hash function, and optimization variables comprising internal state variables of the cryptographic hash function and at least one preimage variable, wherein the at least one constraint is determined from the at least one hash function relation and comprises preceding internal state variables assigned to a preceding iteration; and solving the optimization problem and determining a preimage element of the cryptographic hash function from an optimizing value of the at least one preimage variable.

Abstract: A method for determining a cryptographic key is carried out in a data processing system, and comprises: providing a plaintext and a ciphertext determined from the plaintext using a cryptographic key and a cryptographic procedure which comprises cryptographic operations; for each cryptographic operation of the cryptographic procedure, providing at least one intermediate relation which comprises an intermediate equation and/or an intermediate inequality; determining an optimization problem comprising: the plaintext and the ciphertext; at least one optimization expression assigned to a round of the cryptographic procedure; and optimization variables comprising state variables of the cryptographic procedure and a cryptographic key variable; wherein the at least one optimization expression is determined from the at least one intermediate relation and comprises at least one preceding state variable assigned to a preceding round.