We have designed and developed superconducting single flux quantum (SFQ) digital signal processing circuits using the residue number system (RNS). RNS arithmetic is a complete alternative to binary arithmetic for performing digital computations, which appears to have many advantages for SFQ circuits. We present a scheme for performing all RNS arithmetic functions using Josephson shift registers alone, and suggest that this Is advantageous for high-temperature superconductor computational circuits. We have designed a one-decimal-digit adder, realized with Nb-based superconducting circuitry. Its most complex component, the mod5 adder, has been simulated to show perfect functionality and subcell simulated margins are compared with the experimental results.>We have designed and developed superconducting single flux quantum (SFQ) digital signal processing circuits using the residue number system (RNS). RNS arithmetic is a complete alternative to binary arithmetic for performing digital computations, which appears to have many advantages for SFQ circuits. We present a scheme for performing all RNS arithmetic functions using Josephson shift registers alone, and suggest that this Is advantageous for high-temperature superconductor computational circuits. We have designed a one-decimal-digit adder, realized with Nb-based superconducting circuitry. Its most complex component, the mod5 adder, has been simulated to show perfect functionality and subcell simulated margins are compared with the experimental results.>

IEEE Transactions on Applied SuperconductivityJun 1, 199511 citations

Superconductivity

David S. Simon

Undergraduate texts in physicsJan 1, 20250 citations

Double-Transmon Coupler: Fast Two-Qubit Gate with No Residual Coupling for Highly Detuned Superconducting Qubits

Hayato Goto

Tunable couplers, which turn on and off the interaction between qubits, have emerged as a key means to achieve low error rates in superconducting quantum computers. Conventional devices using one transmon qubit exhibit unwanted residual coupling, though, especially at the high detuning that is desirable for suppressing crosstalk errors. To solve this critical problem, the author proposes a tunable coupler based on two transmons that satisfies the ideal conditions of no residual coupling and fast two-qubit gate operations at high detuning. This double-transmon coupler is expected to become standard for superconducting architectures by eliminating unwanted coupling during idle time.Tunable couplers, which turn on and off the interaction between qubits, have emerged as a key means to achieve low error rates in superconducting quantum computers. Conventional devices using one transmon qubit exhibit unwanted residual coupling, though, especially at the high detuning that is desirable for suppressing crosstalk errors. To solve this critical problem, the author proposes a tunable coupler based on two transmons that satisfies the ideal conditions of no residual coupling and fast two-qubit gate operations at high detuning. This double-transmon coupler is expected to become standard for superconducting architectures by eliminating unwanted coupling during idle time.

arXiv:2203.11451Physical Review AppliedSep 15, 202235 citations

Double superconductivity

David Abergel

Nature PhysicsOct 1, 20210 citations

Relationship between the pseudo- and superconducting gaps: Effects of residual pairing correlations below Tc

Ioan Kosztin, Qijin Chen, Boldizsár Jankó +1 more

The existence of a normal-state spectral gap in underdoped cuprates raises important questions about the associated superconducting phase. For example, how does this pseudogap evolve into its below ${T}_{c}$ counterpart? In this paper we characterize this unusual superconductor by investigating the nature of the ``residual'' pseudogap below ${T}_{c},$ and find that it leads to an important distinction between the superconducting excitation gap and order parameter. Our approach is based on a conserving diagrammatic BCS Bose-Einstein crossover theory which yields the precise BCS result in weak coupling at any $T<{T}_{c}$ and reproduces Leggett's results in the $T=0$ limit. We explore the resulting experimental implications.The existence of a normal-state spectral gap in underdoped cuprates raises important questions about the associated superconducting phase. For example, how does this pseudogap evolve into its below ${T}_{c}$ counterpart? In this paper we characterize this unusual superconductor by investigating the nature of the ``residual'' pseudogap below ${T}_{c},$ and find that it leads to an important distinction between the superconducting excitation gap and order parameter. Our approach is based on a conserving diagrammatic BCS Bose-Einstein crossover theory which yields the precise BCS result in weak coupling at any $T<{T}_{c}$ and reproduces Leggett's results in the $T=0$ limit. We explore the resulting experimental implications.

arXiv:cond-mat/9805065Physical review. B, Condensed matterSep 1, 199871 citations

Switching on Superconductivity

ScienceApr 28, 20000 citations

The existence of a normal-state spectral gap in underdoped cuprates raises important questions about the associated superconducting phase. For example, how does this pseudogap evolve into its below

{T}_{c}

counterpart? In this paper we characterize this unusual superconductor by investigating the nature of the ``residual'' pseudogap below

{T}_{c},

and find that it leads to an important distinction between the superconducting excitation gap and order parameter. Our approach is based on a conserving diagrammatic BCS Bose-Einstein crossover theory which yields the precise BCS result in weak coupling at any

T<{T}_{c}

and reproduces Leggett's results in the

T=0

limit. We explore the resulting experimental implications.