What is claimed is:1. A reciprocal quantum logic (RQL) demultiplexer circuit comprising:respective ports for a selector input, a data input, a first output, and a second output;a selector Josephson junction connected between a first node and a circuit ground and configured to trigger upon assertion of a selector input signal from the selector input port;first and second circuit branches diverging from the first node and converging at a second node, the second node being configured to receive the data input at the data input port;wherein the RQL demultiplexer circuit is configured such that non-assertion or assertion of the selector signal respectively selects between:a signal arriving on the data input port being propagated through the first circuit branch to the first output port, orthe signal arriving on the data input port being propagated through the second circuit branch to the second output port.2. The RQL demultiplexer circuit of claim 1, wherein the first circuit branch comprises:a first inductor connected between the first node and a third node;a pulse generator connected to the third node, the pulse generator comprising two Josephson junctions and an AC bias source;an escape Josephson junction connected between the third node and a fourth node; anda first output Josephson junction connected between the fourth node and the circuit ground.3. The RQL demultiplexer circuit of claim 1, wherein the second circuit branch comprises:a second inductor connected between the first node and a fifth node;a second output Josephson junction connected between a sixth node and the circuit ground; anda third output Josephson junction connected between the fifth node and the circuit ground.4. The RQL demultiplexer circuit of claim 1, wherein:the first circuit branch comprises:a first inductor connected between the first node and a third node;a pulse generator connected to the third node, the pulse generator comprising two Josephson junctions and an AC bias source;an escape Josephson junction connected between the third node and a fourth node; anda first output Josephson junction connected between the fourth node and the circuit ground; andthe second circuit branch comprises:a second inductor connected between the first node and a fifth node;a second output Josephson junction connected between a sixth node and the circuit ground; anda third output Josephson junction connected between the fifth node and the circuit ground.5. The RQL demultiplexer circuit of claim 4, wherein the demultiplexer circuit is configured such that non-assertion or assertion of the selector signal respectively selects between:a signal arriving on the data input port being propagated through the fourth node to the first output port, orthe signal arriving on the data input port being propagated through the sixth and fifth nodes to the second output port.6. The RQL demultiplexer circuit of claim 4, further comprising:a third inductor connected between the second node and the fourth node in the first circuit branch;a fourth inductor connected between the second node and the sixth node in the second circuit branch; anda fifth inductor connected between the sixth node and the fifth node in the second circuit branch.7. The RQL demultiplexer circuit of claim 1, further comprising a Josephson transmission line (JTL) between the data input port and the second node.8. The RQL demultiplexer circuit of claim 1, having no more than twelve inductors, exclusive of any inductors in input or output Josephson transmission lines (JTLs).9. The RQL demultiplexer circuit of claim 1, having no more than seven Josephson junctions, exclusive of any Josephson junctions in input or output Josephson transmission lines (JTLs).10. The RQL demultiplexer circuit of claim 1, having no more than seven Josephson junctions and no more than twelve inductors, exclusive of any Josephson junctions or inductors in input or output Josephson transmission lines (JTLs).