Optimization of shadow evaporation and oxidation for reproducible quantum Josephson junction circuits

Moskalev, Dmitry O.; Zikiy, Evgeniy V.; Pishchimova, Anastasiya A.; Ezenkova, D. A.; Smirnov, Nikita S.; Ivanov, Anton I.; Korshakov, Nikita D.; Rodionov, Ilya A.

doi:10.1038/s41598-023-31003-1

Cited by 9 publications

(5 citation statements)

References 46 publications

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“…Secondly, the JJ fabrication process: Place the sample in the coating machine, in the position of the first evaporation angle (θ 1 = + 54°), then begin coating the lower Al film (thickness = 100 nm). The AlO x layer was obtained by oxidising the top of the first Al film in pure oxygen at a pressure of 3.2 mbar for 10 min 89 . Then, switch the sample position to the second evaporation angle (θ 2 = − 54°) and start coating the upper Al film (thickness = 120 nm), as shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

Josephson radiation threshold detector

Ali,

Ouyang,

et al. 2024

Sci Rep

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A Josephson radiation threshold detector (JRTD) that is based on the threshold behaviour of a current bias Josephson junction (CBJJ) is designed and fabricated for infrared radiation (IR@1550nm) detection at low temperatures. To achieve the optimal performance, we develop a binary hypothesis detection method to calibrate Josephson threshold behaviours (i.e. the switching current distributions of the CBJJ with the Al/AlOx/Al junction) in the absence and presence of radiation. In the absence of IR radiation, the junction transitioned with a measurable voltage drop across the junction, and this signal was treated as the events of hypothesis H0. The events of junction transition observed in the presence of the IR radiation served as hypothesis H1. Considering the usual Gaussian noise and based on statistical decision theory, the accumulated data of the measured switching current distributions are processed, and the threshold sensitivity of the demonstrated JRTD device is estimated. The minimum detectable IR radiation power of the proposed detector is approximately 0.74 pW, which corresponds to the photon rate of 5.692 × 106 photons/second. Further optimisation of JRTDs to implement the desired binary detection of a single photon is still a subject of argument, at least theoretically.

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Section: Methodsmentioning

confidence: 99%

Josephson radiation threshold detector

Ali,

Ouyang,

et al. 2024

Sci Rep

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“…Three qubits on the chip have the leads fabricated together with the SQUID loop using lift-off process as in Ref. 42 , 43 . The leads of the other three qubits were patterned using optical lithography and then wet-etched together with the capacitor pads.…”

Section: Resultsmentioning

confidence: 99%

Wiring surface loss of a superconducting transmon qubit

Smirnov,

Krivko,

Solovyova

et al. 2024

Sci Rep

Self Cite

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Quantum processors using superconducting qubits suffer from dielectric loss leading to noise and dissipation. Qubits are usually designed as large capacitor pads connected to a non-linear Josephson junction (or SQUID) by a superconducting thin metal wiring. Here, we report on finite-element simulation and experimental results confirming that more than 50% of surface loss in transmon qubits can originate from Josephson junctions wiring and can limit qubit relaxation time. We experimentally extracted dielectric loss tangents of qubit elements and showed that dominant surface loss of wiring can occur for real qubits designs. Finally, we experimentally demonstrate up to 20% improvement in qubit quality factor by wiring design optimization.

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“…Also, the roughness strongly depends on the deposition rate. The oxidation process affects the barrier properties as well; perhaps with dynamic oxidation [ 26 ] (with constant pumping) one can try to achieve better results.…”

Section: Resultsmentioning

confidence: 99%

Measurements of dichroic bow-tie antenna arrays with integrated cold-electron bolometers using YBCO oscillators

Revin,

Pimanov,

Chiginev

et al. 2024

Beilstein J. Nanotechnol.

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We consider properties of dichroic antenna arrays on a silicon substrate with integrated cold-electron bolometers to detect radiation at frequencies of 210 and 240 GHz. This frequency range is widely used in cosmic microwave background experiments in space, balloon, and ground-based missions such as BICEP Array, LSPE, LiteBIRD, QUBIC, Simons Observatory, and AliCPT. As a direct radiation detector, we use cold-electron bolometers, which have high sensitivity and a wide operating frequency range, as well as immunity to spurious cosmic rays. Their other advantages are the compact size of the order of a few micrometers and the effect of direct electron cooling, which can improve sensitivity in typical closed-loop cycle 3He cryostats for space applications. We study a novel concept of cold-electron bolometers with two SIN tunnel junctions and one SN contact. The amplitude–frequency characteristics measured with YBCO Josephson Junction oscillators show narrow peaks at 205 GHz for the 210 GHz array and at 225 GHz for the 240 GHz array; the separation of these two frequency bands is clearly visible. The noise equivalent power level at an operating point in the current bias mode is 5 × 10−16 W/√Hz.

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Optimization of shadow evaporation and oxidation for reproducible quantum Josephson junction circuits

Cited by 9 publications

References 46 publications

Josephson radiation threshold detector

Josephson radiation threshold detector

Wiring surface loss of a superconducting transmon qubit

Measurements of dichroic bow-tie antenna arrays with integrated cold-electron bolometers using YBCO oscillators

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