A high voltage pulse generator is presented to drive Pockels cell. The Pockels cell behaves like a capacitor which slows the rise/fall time of the pulse and restrains the repetition rate of the generator. To drive the Pockels cell applied in quantum communication system, it requires about 1 MHz repetition rate with the rise/fall time of the pulse less than 50 ns, adjustable amplitude up to 800 V and an adjustable duration. With the assistance of self-designed transformers, the circuits is simplified that a pair of high current radio frequency (RF) MOSFET drivers are employed to switch the power MOSFETs at a high speed, and the power MOSFETs shape the final output pulse with the requirements. From the tests, the generator can produce 800 V square pulses continously at 1 MHz rate with 46 ns in risetime and 31 ns in falltime when driving a 51 pF capacitive load. And the generator is now used to drive Pockels cell for encoding the polarization of photons.
A high voltage pulse generator is presented to drive Pockels cell. The Pockels cell behaves like a capacitor which slows the rise/fall time of the pulse and restrains the repetition rate of the generator. To drive the Pockels cell applied in quantum communication system, it requires about 1 MHz repetition rate with the rise/fall time of the pulse less than 50 ns, adjustable amplitude up to 800 V and an adjustable duration. With the assistance of self-designed transformers, the circuits is simplified that a pair of high current radio frequency (RF) MOSFET drivers are employed to switch the power MOSFETs at a high speed, and the power MOSFETs shape the final output pulse with the requirements. From the tests, the generator can produce 800 V square pulses continously at 1 MHz rate with 46 ns in risetime and 31 ns in falltime when driving a 51 pF capacitive load. And the generator is now used to drive Pockels cell for encoding the polarization of photons.
A suitable data link from RSFQ to semiconductor electronics remains challenging. We report an output amplifier that uses a new pulse multiplier circuit. The pulse multiplier consists of several stages arranged in series; a double-flux-quantum gate at each stage promotes the SFQ pulse to the next stage. Characteristics of the circuit design are: 1) DC power. As with the DFQ gate, every unshunted Josephson junction in the amplifier is loaded by critically-damped junctions that prevent voltage-state modes. 2) Equal rise and fall times that scale with output amplitude. In our case, 50 ps rise and fall time and 1-2 mV output amplitude can be realized, which is ideal for a data rate of 10 Gb/s. 3) Quantum accurate voltage multiplication independent of bias current. 4) Non-return-to-zero (NRZ) operation. The circuit was designed and successfully tested in our 8 kA/cm/sup 2/ foundry process. A 60 GHz pulse train, generated on-chip, was gated with RSFQ logic to produce a data pattern that was then fed into a pulse multiplier of either ten or twenty stages. Voltage multiplication was observed with operating margins of /spl plusmn/21% on bias current. Fast rise time was directly observed; unfortunately, fall time was spoiled by ringing on a 1 ns time scale. It is plausible that small changes to the physical layout of the circuit would produce desired operation.
Abstract A simple short-pulse generator circuit based on electronic gates is designed for short electric pulse of about 12 ns at Full Width at Half Maximum (FWHM) and 3.6 Volt amplitude for driving a laser diode. Using our circuit with a 780 nm laser diode designed and fabricated for producing short light pulses. The circuit utilizes an AND gate, a XOR gate, and a common function generator, provides a repetition rate from DC up to 1 MHz. The laser pulses were generated and then detected via an avalanche photodiodes (APD). This finding can benefit the field of light-based quantum information including single photon experiments.
Quantum key distribution (QKD) offers the ability of information theoretic security key exchange. The secure key rate is an important indicator for the practical QKD systems, which determines what kinds of applications can be supported. One most effective way to enhance the secure key rate is to increase the system repetition frequency. Here, we report an implementation of a high-speed DC-coupled modulator driving circuit with a repetition rate of up to 5 GHz. The circuit outputs a multi-amplitude return-to-zero pattern pulse with a maximum amplitude of 7.5 V. The design adapts to the various electro-optic modulators widely employed in QKD systems. The minimum pulse width is measured as 75 ps, with the relative noise level less than 1.5% for all the output amplitudes under random modulation.
Abstract Quantum technologies is an emerging field of physics and engineering based on exploiting properties of quantum mechanics such as entanglement, superposition, or tunneling, and which is expected to impact many applications, such as communications, simulation, computation, or sensing and metrology. The operation of quantum technologies is based on the manipulation of the quantum states of certain devices, either to induce transitions between states or to detect the transitions. Irrespective of the practical realization of these quantum devices, their manipulation requires interacting with their quantum resonant states, for which very narrow radio‐frequency (RF) bursts in the range of the GHz are required. Arbitrary waveform generators are used to generate these signals for test purposes, but this is not suitable for practical quantum technology applications, which will need to produce the required bursts by specific circuit building blocks with low power and small dimensions. Here, an integrated RF burst generator capable of producing GHz bursts shorter than 1 ns is presented. The proposed architecture is tested using a 5 GHz quadrature LC‐tank voltage‐controlled oscillator (LC‐VCO), showing that the four equally spaced phases can be switched every 500 ps, which allows the generation of more complex RF bursts for optimized quantum state manipulation.
We present the design and experimental implementation of a compact high-voltage driver tailored for multi-wave-plate electro-optical polarization controllers (EPC) in polarization-based DV-QKD subsystems. The driver is capable of deriving a 140 Vppoutput swing per wave-plate, supports modulation bandwidths up to 7.5MHz, with 10mV resolution, and incorporates per-channel Analog-to-Digital Converter (ADC) monitoring for real-time feedback. A two-stage architecture, with a low-voltage pre-amplification stage followed by a high-voltage output stage, is used with the input being provided by a 16-channel FMC216 Digital-to-Analog Converter (DAC) board, connected to Xilinx Zynq FPGA. Electrical characterization shows that both rise times (∼30ns) and maximum stable square-wave frequency, up to 7.5 MHz, improve as the input Vppincreases, with output gain scaling linearly with input amplitude. Optical testing demonstrates reliable polarization state stability and speed. By enabling fast, precise State of Polarization (SOP) control without bulky stabilization hardware, our driver significantly simplifies the design of polarization-encoded QKD transmitters and receivers, paving the way toward cost-effective, high-rate quantum communications.
Creating and controlling well-defined single-photon states is important for many quantum enhanced technologies. Information can be encoded in any degree of freedom associated with a single-photon field excitation, for example in the polarization or transverse spatial mode structure. The ability to encode multiple qubits in these states is desirable for high data transmission rates and increased information processing capacity. The spectral-temporal domain offers a large Hilbert space for encoding information, well suited to integrated optical architectures owing to the low cross-talk between channels. Indeed, time-frequency encoding is an integral component of existing information technologies infrastructure. Thus, complete, coherent control of the spectral-temporal mode structure of light is essential to advancing optical quantum technologies. Arbitrary control of single-photon states has been demonstrated in the polarization and spatial-momentum degrees of freedom however, is yet to be established in the spectral-temporal domain. Recently it was shown that spectral-temporal pulse shaping is experimentally feasible using nonlinear optical methods. However, such techniques can introduce noise photons, are challenging to implement deterministically and require specially prepared auxiliary pump pulses. Furthermore, they are typically only possible at relatively low repetition rates to avoid damage of nonlinear optical materials. Here, we demonstrate deterministic pulse shaping of single-photon wave packets by introducing a time-varying phase. Applying linear or quadratic phase to the wave packet introduces a spectral shift or spectral broadening, respectively. Achieving significant spectral manipulation requires temporal-phase modulation on the order of π. The phase must also vary on the same time scale as the optical pulses, approximately 1 ps in duration here. This relatively rapid phase variation is achieved using a fast electro-optic phase modulator. The modulator is driven by a time-varying voltage that is synchronized with a pulse train of single-photon wave packets for accurate temporal phase control. In this thesis, we experimentally demonstrate control of the spectral-temporal state of single-photon wave packets using this method. Heralded single-photon wave packets are generated by spontaneous parametric down conversion pumped by a frequency-doubled Titanium-Sapphire laser oscillator with 80 MHz repetition rate. To achieve significant modulation of single-photon pulses a 10 V peak-to-peak radio-frequency signal of 40 GHz drives the phase modulator, which requires approximately 3.6 V to achieve a π phase shift. The signal is synchronized with the oscillator pulse train using custom designed electronics. Details of these electronics are presented, resulting in a robust phase and amplitude controllable 40 GHz voltage source, phase locked to the single-photon pulse train. To demonstrate the utility of this pulse-shaping method we experimentally show spectral shearing of almost 1 nm for single-photon wave packets with 830 nm central wavelength and 1 nm bandwidth. Measurement of the second-order intensity correlation before and after the wave-packet manipulation remains constant within uncertainty of the measurement, showing that the quantum nature of the single-photon source is not deteriorated by the modulator. Preservation of the wave-packet coherence is verified by two-photon interference between spectrally sheared and non-modulated single-photons.