Effective method of forming and detecting a fractional magnetic flux quantum

Tanaka, Y.; Yamamori, Hirotake; Arisawa, Shunichi

doi:10.1016/j.physc.2021.1353932

Cited by 12 publications

(8 citation statements)

References 62 publications

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“…The fractional flux is generated in the ultrathin bilayer; the fractional value is determined as the ratio of the thickness of the upper layer to the lower layer [14,23]. Fractional flux quanta were confirmed in an ultrathin bilayer system with a hole present only in the upper layer [14,16]. We believe that the same phenomenon may occur in an ultrathin bilayer system with a through-hole.…”

Section: Resultsmentioning

confidence: 70%

“…The value of the fractional quantum can vary when there is a difference in the effective thickness between the lower and upper layers. Considering the proximity effect in the Al layer, the thicknesses of the upper and lower layers of the bilayer were slightly different [14,16]. The amount of shift with 0.45 ± 0.01Φ ̃0 can be explained by this theory.…”

Section: Resultsmentioning

confidence: 84%

“…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%

“…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 . The device temperature was first increased to 12-14 K, which was higher than the critical temperature of superconductivity for the bilayer (i.e., 𝑇 C bilayer = 7.73 K) [14,16]; subsequently, the temperature was reduced following the application of a magnetic field. The magnetic field was then removed at temperatures in the range of 6-6.5 K. After cooling below 5.5 K, we re-applied the field to measure the external field dependency of 𝐼 C at low temperatures.…”

Section: Methodsmentioning

confidence: 99%

“…However, it requires the presence of a person throughout the measurement process, and it is difficult to measure the magnetic field dependence at low temperatures automatically. To investigate the basic properties of an ultrathin bilayer in detail, we placed a direct current superconducting interference device (DC-SQUID) on the ultrathin bilayer with the use of a device process [16]. Given that the structures of qubits and SQUIDs are similar, we believe that our system will facilitate the function of reinforcing/remodeling conventional flux qubits [17].…”

Section: Introductionmentioning

confidence: 99%

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

Ishizu

Yamamori

Arisawa

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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