Superconducting phase shifters have a potential for an enhancement in performances of superconducting singleflux-quantum (SFQ) circuits.In this work, we examined the phase difference in the ground state for two kinds of phase shifters (PSs) with a Josephson -junction using an analog circuit simulator.The effects of an insertion of PSs to an SFQ circuit on its performance were also evaluated. キーワード：超伝導電子デバイス・回路、超伝導位相シフタKeywords：Superconducting electronic devices & circuits, Superconducting phase shifter 1．はじめにSuperconducting phase shifters have a potential for an enhancement in performances of superconducting singleflux-quantum (SFQ) circuits.In this work, we examined the phase difference in the ground state for two kinds of phase shifters (PSs) with a Josephson -junction using an analog circuit simulator.The effects of an insertion of PSs to an SFQ circuit on its performance were also evaluated. キーワード：超伝導電子デバイス・回路、超伝導位相シフタKeywords：Superconducting electronic devices & circuits, Superconducting phase shifter 1．はじめに

Mar 1, 20200 citations

SFQ回路を用いた高スループットなビットスライス乗算器(超伝導マイクロ波応用,信号処理基盤技術及びその応用,一般)

遥平成瀬, 信貴鬼頭, 直史高木

電子情報通信学会技術研究報告. SCE, 超伝導エレクトロニクスJul 6, 20110 citations

量子計算機の可能性-素過程、回路、アルゴリズム

和浩井桁, 信之井元

日本物理学会講演概要集. 秋の分科会Sep 12, 19950 citations

単一磁束量子(SFQ)サンプリング技術の原理と分解能

日高睦夫

応用物理Oct 10, 20030 citations

Current Resolution of a Single-Flux-Quantum Readout Circuit Based on Current-to-Time Conversion Toward a Flux Qubit System

Shoichi Nakamura, H. Numabe, Ali Bozbey +1 more

We study a single-shot single-flux-quantum (SFQ) readout circuit based on current-to-time conversion for superconducting flux qubits. Circulating currents representing states of a qubit were converted to propagation delay time of SFQ pulses, and then detected by a time discriminator. The key parameter which determines the availability of single-shot readout is current resolution. We evaluated the current resolution by measuring the gray zone which was defined as the transition width in the output probability of the current-to-time converter with 1000 trials for each value of an input current. For reducing unwanted effects on the qubit, shunt resistors are required to be removed for Josephson junctions in the readout circuit. We designed two readout circuits for comparison, the circuit composed of shunted junctions and that of unshunted junctions. Gray zones were measured to be 4.8 $\mu{\rm A}$ for unshunted junctions and 2.2 $\mu{\rm A}$ for the shunted ones at 4.2 K. These gray zones may originate from Johnson noise. Operation at a reduced temperature and employment of a likelihood decision circuit will lead to reduced gray zone, i.e., improved current resolution sufficient for single-shot readout.We study a single-shot single-flux-quantum (SFQ) readout circuit based on current-to-time conversion for superconducting flux qubits. Circulating currents representing states of a qubit were converted to propagation delay time of SFQ pulses, and then detected by a time discriminator. The key parameter which determines the availability of single-shot readout is current resolution. We evaluated the current resolution by measuring the gray zone which was defined as the transition width in the output probability of the current-to-time converter with 1000 trials for each value of an input current. For reducing unwanted effects on the qubit, shunt resistors are required to be removed for Josephson junctions in the readout circuit. We designed two readout circuits for comparison, the circuit composed of shunted junctions and that of unshunted junctions. Gray zones were measured to be 4.8$\mu{\rm A}$for unshunted junctions and 2.2$\mu{\rm A}$for the shunted ones at 4.2 K. These gray zones may originate from Johnson noise. Operation at a reduced temperature and employment of a likelihood decision circuit will lead to reduced gray zone, i.e., improved current resolution sufficient for single-shot readout.

IEEE Transactions on Applied SuperconductivityJun 1, 200914 citations

\mu{\rm A}

for unshunted junctions and 2.2

\mu{\rm A}

for the shunted ones at 4.2 K. These gray zones may originate from Johnson noise. Operation at a reduced temperature and employment of a likelihood decision circuit will lead to reduced gray zone, i.e., improved current resolution sufficient for single-shot readout.