Topic II.A.1.a: Novel Superconducting MgB2 Nanowire Based Qubits Constructed by Scanning Tunneling Microscope Electron Beam Induced Decomposition of Newly developed CVD precursors
Abstract
Nanowire qubit design (Bezryadin): Our central goal was to develop a qubit design that would be compatible with the STM. We developed a prototype, which is a system of suspended SiN nanobridges connected to larger thin film electrodes (Fig.1a and Fig.1d (insert)). The system is compatible with STM. The key test outcomes are: (1) The system can be prepared in more than one quantized state, characterized by different values of the winding number, n, of the phase of the superconducting order parameter. (2) The vorticity n can be controlled with absolute precision by our current manipulation algorithm. (3) The vorticity n is very stable at temperatures below 2 K. The sample (Fig.1a) consists of two nanobridges connected to thin (15 nm Nb) superconducting films (the electrodes). To fabricate the sample, a line-with-break pattern is prepared by e-beam lithography. The trench and nanobridges are etched in SF6 plasma. Subsequent HF wet etching gives the undercut under the bridges. As the nanobridges are ready, a 15 nm Nb is sputtered over them and over the entire substrate. Next, photolithography is used to select the nanowires and define the electrodes. The sample was measured at the temperature T=2 K. The results are summarized below. The voltage-current (V-I) curve is shown in Fig.1c, measured as shown in Fig.1b. The bias current was cycled many times, so that the curve reveals two possible values of the critical current. They correspond to two different vorticity states as is revealed by the magnetic field bias effect on the critical current (Fig.1d). In order to create a definite vorticity state n we apply a bias current larger than the first critical current but lower than the second one. If the sample remain at zero voltage, then the state zero is created. If it switches to the normal state, then the bias current is reduced to zero and the procedure is repeated. As the state zero is created we read it out, also by measuring the critical current.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 07, 2022
- Accession Number
- AD1229450
Entities
People
- Alexey Bezryadin
- Gregory S. Girolami
- John Abelson
- Joseph W Lyding
Organizations
- University of Illinois Urbana–Champaign