Abstract: Entanglement-based QKD systems and methods with active phase tracking and stabilization are disclosed wherein pairs of coherent photons at a first wavelength are generated. Second harmonic generation and spontaneous parametric downconversion are used to generate from the pairs of coherent photons entangled pairs of photons having the first wavelength. Relative phase delays of the entangled photons are tracked using reference optical signals. Classical detectors detect the reference signals while single-photon detectors and a control unit generate a phase-correction signal that maintains the relative phases of phase-delay loops via adjustable phase-delay elements.

Abstract: The invention provides an apparatus and method for time delaying different polarization components of a signal relative to one another, comprising a polarization signal splitter which splits first and second polarization components of an input signal into a first component signal and a second component signal such that said first component signal propagates along a first path and the second component signal propagates along a second path, wherein said first component signal reaches a location relative to when said second component reaches said location at times differing by a delayed time, and use of the apparatus in a communication system. The apparatus may be used for quantum cryptography, to convert a sender's polarization-qubit signal into a signal appropriate for channels and receivers based on phase-encoded schemes.

Abstract: A process for fabricating a metallic component is disclosed. The process includes performing multiple electroforming steps on an object to form metallic layers. The process includes performing between the electroforming steps masking and patterning steps using a non-conductive material. The resulting metallic component has either a single layer or multiple layers of cooling or heat transfer channels, which may be at right angles in adjacent layers. The non-conductive material can be removed during the process by a solvent or by melting. The object on which the metallic component is formed may be a flat or shaped mandrel from which the metallic component can be removed. The metallic component is particularly useful in forming optical components for use in extreme ultraviolet (EUV) systems and in cooling and heat transfer systems.

Abstract: A QKD system (10) having two QKD stations (Alice and Bob) optically coupled by an optical fiber link (FL), wherein Bob includes a variable timing delay arranged between Bob's controller (CB) and modulator (MB) or detector unit (40). A set-up and calibration procedure is performed wherein delay DL2 is adjusted until the timings for the modulator and detector unit (TSB and TS42, respectively) are established. Delay DL2 is then fixed so that the detector unit and modulator operate in a common timing mode that is not changed if the synchronization signal is changed. The timing TSS of the synchronization (sync) signals (SS) sent from Alice to Bob is adjusted to arrive at optimum system performance. Once the QKD system is in operation, because the sync signal can drift, the sync signal timing TSS is dithered maintain optimum QKD system performance.

Abstract: A zone-optimized mirror (MZ) for reflecting extreme ultraviolet (EUV) or X-ray radiation (18) includes a reflective surface (S) having two or more substantially discrete zones (Z1, Z2, . . . Zn) that include respective coatings (C1, C2, . . . Cn). Each coating is configured to optimally reflect a select range of incident angles of the radiation incident thereon. An EUV optical system (10) and an EUV lithography system (200) that includes at least one zone-optimized mirror are also disclosed.

Abstract: Systems and methods for forming a time-averaged line image having a relatively high amount of intensity uniformity along its length is disclosed. The method includes forming at an image plane a line image having a first amount of intensity non-uniformity in a long-axis direction and forming a secondary image that at least partially overlaps the primary image. The method also includes scanning the secondary image over at least a portion of the primary image and in the long-axis direction according to a scan profile to form a time-average modified line image having a second amount of intensity non-uniformity in the long-axis direction that is less than the first amount. For laser annealing a semiconductor wafer, the amount of line-image overlap for adjacent scans of a wafer scan path is substantially reduced, thereby increasing wafer throughput.

Abstract: The line imaging system includes a laser, first and second cylindrical optical systems with a first spatial filter disposed therebetween, a knife-edge aperture, a cylindrical relay system, and a cylindrical focusing lens. The first spatial filter is configured to truncate a line focus within the central lobe to form a first light beam. The second cylindrical lens system is arranged in the far field and is configured to perform spatial filtering to pass central intensity lobes of the first light beam while blocking outlying intensity lobes. The resultant twice-filtered light beam is has a relatively flat-top intensity distribution associated with the long direction of the line image so that subsequent truncation by the knife-edge aperture transmits more light than conventional line imaging systems. A laser annealing system that employs the line imaging system is also disclosed.

Abstract: Apparatus and methods of performing fast single-qubit quantum gates using ultrafast femtosecond frequency chirped laser pulses are disclosed. The use of chirped pulses removes the demanding restrictions of prior art approaches and allows for the construction of fast quantum gates that operate at speeds on the of order several picoseconds. The apparatus includes two synchronized lasers (pump and Stokes) used to manipulate a qubit wave function in a select manner. Each laser system generates a train of optical pulses. Pulse pickers choose pump and Stokes pulses, which propagate though respective pulse shapers that apply necessary time-dependent phases. To achieve complete overlap between the pulses in time domain, necessary adjustments can be made by using an additional time delay line, which can be located in any path or in both paths.

Abstract: A robust, quickly tunable narrow-linewidth entangled photon source system based on Spontaneous Parametric Down Conversion (SPDC) of the pump light in periodically polled LiNbO3 (PPLN) waveguides. The photon source provides narrow-linewidth, entangled output photons having a wavelength in the telecom C-Band wavelength. To tailor the output spectrum of the output photons, the PPLN waveguide is arranged between two end waveguides having LiNbO3-embedded Bragg gratings, thereby forming a tunable Fabry-Perot cavity. The resulting narrow output linewidth of the output photons makes the system desirable for use in a long-distance quantum key distribution (QKD) system.

Abstract: Systems and methods for enhanced quantum key distribution (QKD) using an actively compensated QKD system. The method includes exchanging quantum signals between first and second QKD stations and measuring the quantum signal error. An error signal SE representative of the system visibility error is then generated. An error-signal threshold STH that defines a system visibility error limit is then selected. Those qubits measured with the condition SE>STH are called “above-threshold” qubits, while those qubits measured with the condition SE?STH are called “below-threshold” qubits. Only below-threshold qubits are stored and used to form the final quantum key. This is accomplished by sending a blanking signal SB to the memory unit where the qubits are stored. The blanking signal prevents above-threshold qubits from being stored therein. The raw quantum key so formed has few errors and thus forms a longer final quantum key for a given number of exchanged quantum signals.

Abstract: Linear chirped pulses in a Raman excitation scheme provide selective excitation of only one target transition (single mode) in a molecule without disturbing any other transitions or molecules. Selectivity is guaranteed by the adiabaticity of the pulse excitation, which allows manipulation by only a resonant mode while leaving all of the other modes unperturbed. This in turn allows for enhanced imaging or spectroscopic analysis of a sample that contains one or more of the molecules.

Abstract: Systems and methods for multiplexing two or more channels of a quantum key distribution (QKD) system are disclosed. A method includes putting the optical public channel signal (SP1) in return-to-zero (RZ) format in a transmitter (T) in one QKD station (Alice) and amplifying this signal (thereby forming SP1*) just prior to this signal being detected with a detector (30) in a receiver (R) at the other QKD station (Bob). The method further includes precisely gating the detector via a gating element (40) and a coincident signal (PN1?) with pulses that coincide with the expected arrival times of the pulses in the detected (electrical) public channel signal (SP2). This allows for the public channel signal to have much less power, making it more amenable for multiplexing with the other QKD signals.

Abstract: An afocal Galilean attachment lens is disclosed, with the lens comprising, along an optical axis, a first lens group with overall negative optical power and a second lens group with overall positive power. The first and second lens groups are arranged to define a Galilean configuration. The lens also has exit and an entrance pupils with respective diameters DEX and DEN that define a pupil magnification PM=DEX/DEN>4 and in some embodiments PM>10. The afocal Galilean attachment lens also has a length parameter defined LP>200 and in some embodiments LP>700. The extreme length of the afocal Galilean attachment allows for photographing or filming objects that are remote or otherwise hard to photograph while also providing a relatively large depth of field.

Abstract: A quantum key distribution (QKD) cascaded network with loop-back capability is disclosed. The QKD system network includes a plurality of cascaded QKD relays each having two QKD stations Alice and Bob. Each QKD relay also includes an optical switch optically coupled to each QKD station in the relay, as well as to input ports of the relay. In a first position, the optical switch allows for communication between adjacent relays and in a second position allows for pass-through communication between the QKD relays that are adjacent the relay whose switch is in the first position.

Abstract: The Bell-state analyzer includes a semiconductor device having quantum dots formed therein and adapted to support Fermions in a spin-up and/or spin-down states. Different Zeeman splittings in one or more of the quantum dots allows resonant quantum tunneling only for antiparallel spin states. This converts spin parity into charge information via a projective measurement. The measurement of spin parity allows for the determination of part of the states of the Fermions, which provides the states of the qubits, while keeping the undetermined part of the state coherent. The ability to know the parity of qubit states allows for logic operations to be performed on the qubits, i.e., allows for the formation of (two-qubit) quantum gates, which like classical logic gates, are the building blocks of a quantum computer. Quantum computers that perform a parity gate and a CNOT gate using the Bell-state analyzer of the invention are disclosed.

Abstract: Large aperture optical systems that are extremely well corrected over a large flat field and over a large spectral range are disclosed. Breathing and aberration variation during focusing are optionally controlled by moving at least two groups of lens elements independently. Aberration correction in general is aided by allowing the working distance to become short relative to the format diagonal. Field curvature is largely corrected by a steeply curved concave surface relatively close to the image plane. This allows the main collective elements to be made of low-index anomalous dispersion materials in order to correct secondary spectrum. In wide-angle example embodiments, distortion may be controlled with an aspheric surface near the front of the lens.

Abstract: Methods for calibrating the modulators in a QKD system (100) are disclosed. The methods include setting the voltage (VB) of Bob's modulator (MB) to a positive value and then adjusting the voltage (VA) of Alice's modulator (MA) in both the positive and negative direction to obtain overall relative phase modulations that result in maximum and minimum photon counts (N) in the two single-photon detectors (32a, 32b). Bob's modulator voltage is then set to a negative value and the process repeated. When the basis voltages (VB(1), VB(2), VA(1), VA(2), VA(3) and VA(4)) are established, the QKD system is operated with intentionally selected incorrect bases at Bob and Alice to assess orthogonality of the basis voltages by assessing whether or not the probability of photon detection at the detectors is 50:50. If not, the modulator voltages are adjusted to be orthogonal. This involves changing Bob's basis voltage (VB(1) and/or VB(2)) and repeating the process until a 50:50 detector count distribution is obtained.

Abstract: Systems and methods for quantum secret splitting based on non-orthogonal multi-particle states are disclosed. The method includes preparing at a sender (“Charlie”) two qubits each of which can be in one of two non-orthogonal states and distributing the qubits to respective parties Alice and Bob. The method also includes measuring at Alice the state of the qubit she receives by a projective measurement so that the measurement result is either 0 or 1, and at Bob measuring the state of the qubit he receives such that the measurement result is either 0, 1 or f, wherein f represents a failure by Bob to properly measure the qubit state. The method also includes communicating between Alice, Bob and Charlie the outcome of their respective measurements so as to deduce the state of the qubits sent to Alice and Bob.

Abstract: Key manager systems and methods for a QKD-based network are disclosed. The system includes a QKD layer that generates quantum encryption keys, a persistent storage layer that stores the quantum encryption keys, and a key management layer. The key management layer generates an application registration record that includes a list of multiple applications that use the quantum encryption keys. The key management layer also generates a corresponding key storage layer. The multiple applications reside in an applications layer. The applications in each node remove keys from the key storage layer so that each node can encrypt/decrypt data using quantum encryption keys. The methods also include secure QKD system boot-up and authentication that facilitate implementing a commercial QKD system in real-world environments.

Abstract: A method for enhancing the security of a quantum key distribution (QKD) system having QKD stations Alice and Bob. The method includes encrypting key bits generated by a true random number generator (TRNG) and sent to a polarization or phase modulator to encode weak optical pulses as qubits to be shared between Alice and Bob. Key bit encryption is achieved by using a shared password and a stream cipher. Bob obtains at least a subset of the original key bits used by Alice by utilizing the same stream cipher and the shared password.