Superconducting circuit having an output conversion circuit

A superconducting circuit for performing a logic operation and producing an output indicative of the result of the logic operation with a logic amplitude suitable for processing by an external circuit, comprising:

• a Josephson processing circuit, comprising one or more Josephson devices, for performing the logic operation and for producing an output logic signal having a first logic amplitude corresponding to the logic operation;
• voltage amplification means, supplied with the output logic signal from the Josephson processing circuit, for producing an output signal having a second logic amplitude that is substantially larger than the first logic amplitude, said voltage amplification means comprising a plurality of superconducting quantum interference devices each having a control line coupled magnetically thereto, each of said superconducting quantum interference devices being supplied with a bias current for causing a transition from a superconducting state to a finite voltage state in response to a signal on the control line, said superconducting quantum interference devices being connected in series such that the bias current flows consecutively through the plurality of superconducting quantum interference devices, said output logic signal of the Josephson processing circuit being passed consecutively through the control line of the plurality of superconducting quantum interference devices, for causing the transition from the superconducting state to the finite voltage state in the superconducting quantum interference devices, each superconducting quantum interference device producing an elemental logic amplitude in response to the transition to the finite voltage state, said voltage amplification means producing the output signal having the second logic amplitude as a sum of the elemental logic amplitudes of the plurality of superconducting quantum interference devices;
• and
• impedance conversion means supplied with the output signal of the voltage amplification means for producing the output of the superconducting circuit with an output impedance suitable for transferring to the external circuit, said impedance conversion means having an input impedance, when viewed from the voltage amplification means, which is sufficiently large such that the transition of the superconducting quantum interference devices in the voltage amplification means is not influenced by the presence of the impedance conversion means.