Basic characteristics of a simple single-flux-quantum (SFQ) logic gate using high-Tc material and Josephson junction (NdBa2Cu3O7−δ and focused ion beam junction) have been investigated. The logic gate consists of an rf-superconducting quantum interference device (rf-SQUID) and a dc-SQUID. In the logic gate, elementary SFQ logic operations, such as generating SFQ (dc/SFQ) and providing simultaneous readout (SFQ/dc), have been confirmed up to 50 K. The temperature dependencies of the output voltage level and the critical current-normal resistance (IcRn) product were compared, and the decreasing tendency of the output voltage level for increasing temperature was found to be more rapid than that of the IcRn product.Basic characteristics of a simple single-flux-quantum (SFQ) logic gate using high-Tc material and Josephson junction (NdBa2Cu3O7−δ and focused ion beam junction) have been investigated. The logic gate consists of an rf-superconducting quantum interference device (rf-SQUID) and a dc-SQUID. In the logic gate, elementary SFQ logic operations, such as generating SFQ (dc/SFQ) and providing simultaneous readout (SFQ/dc), have been confirmed up to 50 K. The temperature dependencies of the output voltage level and the critical current-normal resistance (IcRn) product were compared, and the decreasing tendency of the output voltage level for increasing temperature was found to be more rapid than that of the IcRn product.

Applied Physics LettersMay 25, 199811 citations

A 3 bit single flux quantum shift register based on high-Tc bicrystal Josephson junctions operating at 50 K

B. Oelze, B. Ruck, Erik Sodtke +3 more

A 3 bit single flux quantum (SFQ) shift register based on high-Tc bicrystal Josephson junctions has been designed, fabricated, and experimentally tested. The circuit consists of 26 bicrystal Josephson junctions and includes the shift register itself, two dc-SFQ converters, one readout superconducting quantum interference device, serving as a SFQ-dc converter, and three Josephson transmission lines. The correct operation of all circuit components has been demonstrated by low frequency testing at a temperature of 50 K.A 3 bit single flux quantum (SFQ) shift register based on high-Tc bicrystal Josephson junctions has been designed, fabricated, and experimentally tested. The circuit consists of 26 bicrystal Josephson junctions and includes the shift register itself, two dc-SFQ converters, one readout superconducting quantum interference device, serving as a SFQ-dc converter, and three Josephson transmission lines. The correct operation of all circuit components has been demonstrated by low frequency testing at a temperature of 50 K.

Applied Physics LettersFeb 3, 199722 citations

Study on integrated processes for SFQ circuits and superconducting nano-devices

Naoki Kondo, Kyosuke Sano, Tanaka Masamitu +3 more

The Japan Society of Applied PhysicsJul 10, 20190 citations

YBa $_{2}$ Cu $_{3}$ O $_{7-\delta }$ Single Flux Quantum Flip Flop Directly Written With a Focused Helium Ion BeamYBa$_{2}$Cu$_{3}$O$_{7-\delta }$Single Flux Quantum Flip Flop Directly Written With a Focused Helium Ion Beam

Han Cai, Hao Li, Ethan Y. Cho +2 more

Superconducting logic circuits based on low transition temperature (Tc) are attractive due to their intrinsic low power consumption and high operating frequency. They have a wide variety of applications (particularly in future computing), but are difficult to use because they require cooling with liquid helium to operate. The current high Tclogic circuit based on YBa2Cu3O7-δ(YBCO) already has the ability to operate at a temperature above 4 K. However, this material is difficult to integrate into large-scale circuits by the traditional YBCO junction fabrication process. The limits of fabrication methods are the bottleneck stifling this material's potential for integration into logic circuits. As such, in this paper we aim to advance the state of the art in junction fabrication technology. Here we report the demonstration of a high Tcsuperconducting single flux quantum (SFQ) circuit made by a focused helium ion beam that is easily fabricated and can readily be incorporated into a large-scale integration with nano-scale junctions for future applications. An inductively coupled readout superconducting quantum interference device (SQUID) is employed to reduce the circuit complexity. The circuit parameters and performance are discussed.Superconducting logic circuits based on low transition temperature (Tc) are attractive due to their intrinsic low power consumption and high operating frequency. They have a wide variety of applications (particularly in future computing), but are difficult to use because they require cooling with liquid helium to operate. The current high Tclogic circuit based on YBa2Cu3O7-δ(YBCO) already has the ability to operate at a temperature above 4 K. However, this material is difficult to integrate into large-scale circuits by the traditional YBCO junction fabrication process. The limits of fabrication methods are the bottleneck stifling this material's potential for integration into logic circuits. As such, in this paper we aim to advance the state of the art in junction fabrication technology. Here we report the demonstration of a high Tcsuperconducting single flux quantum (SFQ) circuit made by a focused helium ion beam that is easily fabricated and can readily be incorporated into a large-scale integration with nano-scale junctions for future applications. An inductively coupled readout superconducting quantum interference device (SQUID) is employed to reduce the circuit complexity. The circuit parameters and performance are discussed.

IEEE Transactions on Applied SuperconductivityApr 1, 202115 citations

YBa

_{2}

_{3}

_{7-\delta }

Single Flux Quantum Flip Flop Directly Written With a Focused Helium Ion Beam