Reliable packaging of Josephson voltage standard circuit for cryocooler operation

Yamamori, Hirotake; Maruyama, Michitaka; Amagai, Yasutaka; Shimazaki, Takeshi

doi:10.1587/elex.16.20190219

“…The series array of 100 SQUIDs improved the signal-to-noise ratio because of the averaged results of the SQUIDs. We quantified the transport properties of the SQUIDs by using a typical instrument [16,19,20]. The flux quantum was trapped as the temperature decreased and while the temperature passed through the superconducting transition point in the presence of an external field (this phenomenon is called "field cooling" (FC)), hereafter referred to as Φ FC .…”

Section: Methodsmentioning

confidence: 99%

Phase shifter based on an ultrathin superconducting bilayer with a through-hole for a superconducting device

Ishizu

¹

,

Yamamori

²

,

Arisawa

³

et al. 2021

Preprint

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Applying a radian phase shift other than 2π is a key issue for superconducting circuits, such as flux qubits. The magnetic flux is useful when generating a phase shift. However, a quantized magnetic flux accompanying a trapped vortex in a superconductor does not have a phase shifter function. The magnetic flux generated by an external field generates noise. In this study, we propose a phase bias system that does not require an external field during operation. We confirm the phase shift of a direct current superconducting interference device (SQUID) placed on an ultrathin superconducting Nb bilayer with a through-hole by cooling it to a temperature below the superconducting transition temperature with an external field. Although the cause of the phase shift in our system is unclear, we believe that it may be caused by a fractional quantum in the bilayer. When the SQUID is replaced by a qubit, the phase shift can be applied to a phase bias.

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“…The series array of 100 SQUIDs improved the signal-to-noise ratio because of the averaged results of the SQUIDs. We quantified the transport properties of the SQUIDs using a typical instrument [16,19,20]. When all the SQUIDs were in the same 𝐼 C state (high/low state), 𝐼 C ± (10%) ≈ 𝐼 C ± (90%).…”

Section: Methodsmentioning

confidence: 99%

Phase shifter based on an ultrathin superconducting bilayer with a through-hole for a superconducting device

Ishizu

¹

,

Yamamori

²

,

Arisawa

³

et al. 2021

Preprint

Self Cite

0

View full text Add to dashboard Cite

Applying a radian phase shift other than 2π is a key issue for superconducting circuits, such as flux qubits. The magnetic flux is useful when generating a phase shift. However, a quantized magnetic flux accompanying a trapped vortex in a superconductor does not have a phase shifter function. The magnetic flux generated by an external field generates noise. In this study, we propose a phase bias system that does not require an external field during operation. We confirm the phase shift of a direct current superconducting interference device (SQUID) placed on an ultrathin superconducting Nb bilayer with a through-hole by cooling it to a temperature below the superconducting transition temperature with an external field. Although the cause of the phase shift in our system is unclear, we believe that it may be caused by a fractional quantum in the bilayer. When the SQUID is replaced by a qubit, the phase shift can be applied to a phase bias.

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“…The residual thermal resistance is not low enough in the most demanding conditions and particular care is required in the design of a chip carrier to reduce thermal gradients, mainly at the interfaces between solid bodies. For JVSs working in the high-vacuum environment of a cryocooler, special cryopackages have been designed [6][7][8][9], exhibiting thermal resistances between chip and cold heat sink of few kelvin per watt. The case of JVS is particularly interesting and challenging: power levels of some tens of milliwatt are generally dissipated within a JVS, possibly causing its actual temperature to differ from that measured with the the sensor by hundreds of millikelvin.…”

Section: Introductionmentioning

confidence: 99%

Using a Josephson junction as an effective on-chip temperature sensor

Durandetto¹,

Sosso²

2021

Supercond. Sci. Technol.

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Temperature sensing and control are essential in experiments running in cryocooled systems, as with the case of liquid helium-free superconducting devices. A Josephson junction as on-chip temperature sensor operated in ac provides the highest sensitivity and minimal power loading to the cryogenic environment, thanks to the noise rejection of lock-in detection. To demonstrate the advantages of on-chip sensing, we tested it with a Josephson voltage standard array in cryocooler and compared with the conventional case of a sensor on the cold surface of the refrigerator, showing that the power dissipated within the chip may further increment the device temperature up to some tenths of kelvin. An ac Josephson junction sensor is proven to be capable of directly stabilizing the temperature of the superconductive circuit from fluctuations of dissipated power during operation. Reliability issues related to flux trapping are discussed and solutions are proposed suited to different applications. Overall, on-chip control with ac Josephson temperature sensing has the advantage of avoiding the complexities in minimization of cryogenic thermal links, virtually reducing to zero the contact resistance and keeping the operating temperature of the superconductor constant, independently of instantaneous operating power.

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Reliable packaging of Josephson voltage standard circuit for cryocooler operation

Cited by 6 publications

References 32 publications

Phase shifter based on an ultrathin superconducting bilayer with a through-hole for a superconducting device

Phase shifter based on an ultrathin superconducting bilayer with a through-hole for a superconducting device

Phase shifter based on an ultrathin superconducting bilayer with a through-hole for a superconducting device

Using a Josephson junction as an effective on-chip temperature sensor

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