Rapid-Single-Flux-Quantum (RSFQ) circuits, in which information is stored in superconductor loops as tiny magnetic flux quanta and transferred as several. The authors study the frequency dependent damping in rapid single flux quantum (RSFQ) circuits as means to reduce dissipation and. Unclassified // For Offical Use Only. 15 March Anna Herr. Rapid Single Flux Quantum Logic. Based on lectures at Chalmers University of Technology.


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If the rapid single flux quantum bias current Ib is not too far from the critical value Ic, this SFQ pulse can be triggered by an incoming short pulse, with either the nominal or a somewhat different amplitude.

It means that the circuit shown in Fig.


On the other hand, if the input pulse is too weak e. After the 2 -jump of the Josephson phase is triggered in the left junction J1 by the input signal, the resulting SFQ pulse developed across J1 will trigger the 2 -jump in Rapid single flux quantum, and this process will continue until the pulse is reproduced at the right edge of the JTL.

For that, critical currents of the junctions and rapid single flux quantum corresponding dc bias currents should grow in the direction of the pulse propagation, with the proportional decrease of the inductances.

If amplification of SFQ pulses is not needed, they can be passed along passive superconducting microstrip lines. Recently, such circuits were used to demonstrate transfer of 5-ps SFQ pulses over distances up to 1 cm without noticeable attenuation - see Polonsky et al.

An evident generalization of the JTL Fig. All these simplest circuits are reciprocal, and cannot be used for isolation, so one needs a buffer stage Fig. In this circuit, critical current of the junction J2 is somewhat smaller than that of the rapid single flux quantum J1.

Now, if the initial pulse arrives from the circuit input A, it is applied to J1 alone, and triggers the 2 -jump of the Josephson phase in J1, leaving the phase across J2 virtually undisturbed.

As a consequence, the SFQ pulse is reproduced and passed to the output terminal B. On the contrary, if a pulse arrives from the latter terminal, it triggers a current pulse in both J1 and Rapid single flux quantum. Hence, voltage across J1 remains close to zero, which means that the SFQ pulse does not reach the input terminal A.

Figure 2e shows a useful recent synthesis of the JTL and the buffer stage, having larger parameter tolerances - see Polonsky et al. The simplest components of RSFQ circuits: After Mukhanov et al. A disadvantage of this circuit is that rapid single flux quantum pulse should be very short e.

A much less demanding way is to use a Josephson junction in parallel with the superconducting inductor L i. In order to generate a single SFQ pulse, the interferometer may be fed by a usual dc current pulse, with only amplitude but not length within certain limits.

Rapid single flux quantum

If its input current I is increased beyond a certain threshold value Iupthe critical state of the junction J3 is achieved, and the SFQ pulse is generated across it. Simultaneously, the three-junction interferometer J1-J3, L1-L3 is switched into another flux state.

In order to reset the interferometer into its initial state, the current should then be decreased below a value Idown at which the 2 -jumps are triggered sequentially in the junctions J1 and J2. The reset is rapid single flux quantum by generation of SFQ pulses across these junctions, which do not penetrate into the output JTL.

Numerical simulations and experiments by Polonsky et al. After Polonsky et al. In rapid single flux quantum words, one of these states corresponds to an additional single flux quantum trapped in the superconducting loop of the interferometer.

Rapid single flux quantum - Wikipedia

Let us suppose that the persistent current is circulating counterclockwise binary 0so that it sums with I in J3: As a result of the jump, the cell is switched to its opposite state 1 with the clockwise circulation of the persistent current.

The auxiliary junctions J1 and J2 defend the SFQ pulse sources from the back reaction of the interferometer in the case of a "wrong" signal, for example, the S set pulse arriving during the state 1.

In this case, junction J2 rather than J3 switches; in other words, the incoming single flux quantum "falls out" of the circuit through J2 if the interferometer loop is unable to accept it.

SFQ pulses can be trapped by this circuit, so that the rapid single flux quantum about their arrival can be conveniently stored there in the form of static magnetic flux, and released when necessary in SFQ pulse form. Figure 4b shows an SFQ analog of the T flip-flop i.