Abstract: Systems and methods are described herein for an electro-absorption modulator (EAM) device. An example EAM device comprises an optical waveguide comprising a waveguide core configured to facilitate propagation and modulation of an optical signal therethrough; a segmented structure comprising diode segments disposed on the waveguide; and an electrical transmission line operatively coupled to the diode segments. The electrical transmission line is configured to facilitate propagation of an electrical signal therethrough. The electrical transmission line includes a first transmission line rail and a second transmission line, where a first subset of diode segments is operatively coupled to the first transmission line rail and a ground rail, and a second subset of diode segments is operatively coupled to the second transmission line and the ground rail. The diode segments from the first subset are disposed alternately with the diode segments from the second subset.

Abstract: Processes and devices for continuous compositional grading in photodetectors and electro-absorption modulators (EAM) are provided. An example photodetector includes a multi-layered structure comprising a collector region, an absorber region, a grading layer, and a peripheral layer, all aligned along a detection axis. The grading layer, positioned adjacent to the absorber region, includes multiple sub-layers that define a continuous compositional grading to facilitate smooth carrier transport and reduce recombination. Similarly, an example electro-absorption modulator (EAM) device includes a waveguide mesa formed on a semiconductor substrate, comprising a multi-quantum well (MQW) core layer, upper and lower near-core cladding layers, and upper and lower central cladding layers. The EAM device features both upper and lower grading layers, each positioned between the near-core cladding layers and the adjacent central cladding layers.

Abstract: Processes for continuous compositional grading for realization of low charge carrier barriers in electro-optical heterostructure semiconductor devices are provided. An example process includes forming, onto one or more semiconductor layers of an electro-optical semiconductor device, a first semiconductor layer associated with a first bandgap value and forming, onto the first semiconductor layer, a grading layer associated with a continuous compositional grading. The example method further includes forming, onto the grading layer, a second semiconductor layer associated with a second bandgap value. The second bandgap value is different than the first bandgap value.

Abstract: Systems and methods are described herein for an electro-absorption modulator (EAM) device. An example EAM device comprises an optical waveguide comprising a waveguide core configured to facilitate a propagation of an optical signal therethrough; a segmented traveling wave electrode structure comprising electrode segments disposed on the optical waveguide; and an electrical transmission line operatively coupled to the electrode segments via conducting bridges, wherein the electrical transmission line is configured to facilitate a propagation of an electrical signal therethrough, wherein the electrode segments are configured to overcome bandwidth and extinction ratio constraints of a lumped EAM.

Abstract: Systems and methods are described herein for an electro-absorption modulator (EAM) device. An example EAM device comprises an optical waveguide comprising a waveguide core configured to facilitate propagation of an optical signal therethrough; a segmented structure comprising diode segments disposed on the waveguide; and a differential electrical transmission line operatively coupled to the diode segments. The electrical transmission line includes a first transmission rail and a second transmission rail, and the electrical transmission line is configured to facilitate propagation of an electrical signal therethrough. The EAM device is configured for operation by a differential radio frequency (RF) source that is configured to supply the electrical signal to the EAM device, and the EAM device is formed on a semi-insulating substrate.

Abstract: Methods, apparatus, and computer program products for quantum communications and quantum information processing are provided. An example method includes determining a received state of a qubit received via a quantum communication link where the received state includes one or more properties of the received qubit. The method further accesses a transmitted state of the qubit where the transmitted state includes one or more properties of the qubit as transmitted. The method continues by comparing the one or more properties of the qubit in the received state with the one or more properties of the qubit in the transmitted state. Finally, the method detects a condition of the quantum communication link based on the comparison between the received state and the transmitted state. In doing so, the embodiments operate to characterize the noise level, security, etc. of a quantum communication interconnect, link, or channel.

Abstract: Various embodiments of the present disclosure are directed to accessing a quantum communication channel undetected and/or characterizing this communication channel based upon attempted access. An example method includes accessing a quantum communication channel transmitting one or more qubits. The method includes the introduction of a noise signal to the quantum communication channel and then applying in its absence one or more weak or variable-strength measurements to the quantum communication channel. A strength of at least one measurement of the one or more measurements is based at least in part upon the current noise signal. The method further includes obtaining information associated with the one or more qubits based on the one or more measurements.

Abstract: Embodiments are disclosed for providing quantum-classical hybrid security. An example system includes a hybrid quantum-classical transmitter device. The hybrid quantum-classical transmitter device includes a classical transmitter and a quantum transmitter. The classical transmitter is configured to generate data based on a cryptography technique. The classical transmitter is also configured to generate a classical bitstream representation of the data, where the classical bitstream is configured for transmission via an optical communication channel. The quantum transmitter is configured to embed one or more qubits into the classical bitstream to generate a hybrid quantum-classical bitstream for transmission via the optical communication channel.

Abstract: Photodetectors configured to detect light in a particular wavelength range and including a quaternary material are described herein. In some embodiments, the present invention may be directed to a photodetector that includes a collector material that is substantially transparent to the particular wavelength range and a quaternary material adjacent to the collector material, where the quaternary material functions as an absorber material and is lattice-matched to the collector material. A conduction band difference between the collector material and the quaternary material may be approximately zero. Additionally, or alternatively, the photodetector may include a peripheral layer adjacent to the quaternary material, where the peripheral layer is doped with carbon. In some embodiments, the photodetector may include an optical window configured for use with a multi-mode optical fiber.

Abstract: Processes for continuous compositional grading for realization of low charge carrier barriers in electro-optical heterostructure semiconductor devices are provided. An example process includes forming, onto one or more semiconductor layers of an electro-optical semiconductor device, a first semiconductor layer associated with a first bandgap value and forming, onto the first semiconductor layer, a grading layer associated with a continuous compositional grading. The example method further includes forming, onto the grading layer, a second semiconductor layer associated with a second bandgap value. The second bandgap value is different than the first bandgap value.

Abstract: Bi-directional quantum interconnects are provided that include a first communication module and a second communication module. The first communication module includes a first quantum transmitter and a first quantum receiver, and the second communication module includes a second quantum transmitter and a second quantum receiver. The example interconnect further includes a first communication medium communicably coupling the first communication module and the second communication module such that communication is provided between the first quantum transmitter and the second quantum receiver and between the second quantum transmitter and the first quantum receiver via the first communication medium. The first quantum transmitter and the second quantum transmitter generate qubits having first and second quantum characteristics, respectively, to allow for bi-directional quantum communication over a common channel.

Abstract: High bandwidth (e.g., >100 GHz) modulators and methods of fabricating such are provided. An optical modulator comprises transmission lines configured to provide a respective radio frequency signal to a respective plurality of segmented capacitive loading electrodes; pluralities of segmented capacitive loading electrodes in electrical communication with a respective one of the transmission lines and in electrical communication with an interface layer of a semiconductor waveguide structure; and the semiconductor waveguide structure. The semiconductor waveguide structure is configured to modulate an optical signal propagating therethrough based at least in part on the respective radio frequency signal. The semiconductor waveguide structure comprises the interface layer, which (a) comprises a semiconductor material and (b) is configured such that an interface resistance of the modulator is ?4 Ohms.

Abstract: High bandwidth (e.g., > 100 GHz) modulators and methods of fabricating such are provided. An EAM comprises a waveguide mesa comprising a continuous multi-quantum well (MQW) layer; a plurality of electrode segments disposed on the waveguide mesa; and a microstrip transmission line disposed on an insulating material layer and in electrical communication with the plurality of electrode segments via conducting bridges. The waveguide mesa comprises alternating active sections and passive sections. An electrode segment of the plurality of electrodes is disposed on a respective one of the active sections. Portions of the continuous MQW layer disposed in each of the active sections having an energy gap defining an active energy gap value. Portions of the continuous MQW layer disposed in each of the passive sections having an energy gap defining an passive energy gap value. The active energy gap value is less than the passive energy gap value.

Abstract: High bandwidth (e.g., > 100 GHz) modulators and methods of fabricating such are provided. An optical modulator comprises transmission lines configured to provide a respective radio frequency signal to a respective plurality of segmented capacitive loading electrodes; pluralities of segmented capacitive loading electrodes in electrical communication with a respective one of the transmission lines and in electrical communication with an interface layer of a semiconductor waveguide structure; and the semiconductor waveguide structure. The semiconductor waveguide structure is configured to modulate an optical signal propagating therethrough based at least in part on the respective radio frequency signal. The semiconductor waveguide structure comprises the interface layer, which (a) comprises a semiconductor material and (b) is configured such that an interface resistance of the modulator is ? 4 Ohms.