The unshunted single-flux-quantum SFQ comparator is described for the first time. Its dynamic behavior is surprisingly similar to the familiar resistively-shunted SFQ comparator. For certain parameter ranges both junctions of the comparator may pulse at the same time to create a reflected anti-pulse. This phenomenon is utilized in a new SFQ comparator design with better coherence properties for qubit readout. Considerations of quantum noise for the unshunted SFQ comparator are discussed.
Simple RSFQ gates can be very robust, and o g erate up to high clock speeds in simulation. Larger RSFQ circuits are generally much more limited in clock speed. We believe that this is partly due to less than optimal choice of the timing inter-connections between gates. Timing design is especially problematic for circuits including data loops (feedback). We have developed a new technique for timing design of RSFQ data loops which may be called "balanced skew clock scheduling." It involves equalizing the minimum clock period between every pair of gates. Mathematical analysis proves the optimality of this scheme and reveals the global timing constraints unique to RSFQ data loops. We used this technique for the design of a simple useful clocked RSFQ circuit, a four-bit pseudo-random number generator (PRNG). Constructed from our standard library cells for a 3.5um 1000A/cm2 Nb-trilayer process, the PRNG worked up to 6 0 GHz in Jspice simulation.
Articles you may be interested inDispersion and dipolar orientational effects on the linear electroabsorption and electrooptic responses in a model guest/host nonlinear optical system Degenerate four wave mixing in Jaggregates of pseudoisocyanine chloride in the presence of exciton annihilation and reversible aggregate disordering AIP Conf.Effects of static disorder and interaction with phonons on the dynamics of Frenkel excitons in molecular aggregates are studied by calculating the absorption of a weak probe in the presence of a strong resonant and off-resonant pump field. To second order in the pump amplitude, the self-energy which determines the Stark shift and dynamical broadening of the probe absorption is expressed in terms of the single exciton Green function and the two-exciton scattering matrix. For stronger pump intensities the self-energy is calculated using higher-order optical response functions of the system.
One of the main difficulties in observing quantum coherence (MQC) in rf-SQUID based systems is extremely short coherence times.Quantum coherence in macroscopic system is rapidly destroyed by interaction with the environment. This precludes any MQC experiments from using high-speed data acquisition that allows direct evidence of coherent evolution of linear combination of rf-SQUID eigenstates. In order to perform such experiments, isolation structures that effectively shield MQC experimental elements from small-signal interaction with data acquisition circuitry on chip and at the same time allow large signals such as RSFQ pulses to propagate through. We consider design and simulation of series of Josephson junctions with varied parameters as an example of such isolation filters.
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