High-resolution superconducting single-flux quantum comparator for sub-Kelvin temperatures

Abstract

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Verification of stable operation of rapid single flux quantum devices with frequency-dependent dissipation

“…The realizability and stability together set an upper limit for I c . Low I c is favourable also in terms of minimal self-heating of RSFQ components [7]- [9]. In qubit applications the effect of the dissipation from the RC shunts 7 DEUTSCHE PHYSIKALISCHE GESELLSCHAFT on the decoherence should be taken into account [14].…”

“…The basic question is to develop devices with sufficient functionality, which also preserve quantum coherence. The generic issues that have been addressed from the RSFQ side include fabrication [5,6] and design [7,8] solutions to decrease self-heating [9] as well as the control of the level of dissipation. The latter is important since the classical interface acts as a dissipative environment for a qubit.…”

Single flux quantum circuits with damping based on dissipative transmission lines

“…is the material constant) may significantly exceed the bath temperature even at low f [5]. The efficient method proposed in Ref.…”

“…The efficient method proposed in Ref. [5] of reducing T e was based on the application of bulky metallic reservoirs (Λ f ≈ 4 × 10 5 µm 3 ), so-called cooling fins, attached to the small resistors. The volume of the RC line shunts designed in our paper is Λ RC ≈ 284 µm 3 ≈ 30Λ R , and this increased volume should result in an approximately twofold (30 1 5 ≈ 2) reduction in their electron temperature T e without attaching them to cooling fins.…”

“…Moreover, the capability of the RSFQ circuits to function at the same low temperature as the qubits is another advantage of this approach. Among these RSFQ circuits are the balanced comparators [4,5,6], SQUIDs [7], the ballistic Josephson Transmission Lines (JTL) [8,9] enabling quantum readout of the qubit, and the RSFQ circuits generating signals controlling the qubit state [10,11].…”