3D nanoSQUID based on tunnel nano-junctions with an energy sensitivity of 1.3 h at 4.2 K

Abstract

We report the performance of a reliable three-dimensional nanometer-sized Superconducting QUantum Interference Device (SQUID). The use of superconductor-isolator-superconductor Nb/ Al-AlO x /Nb Josephson tunnel junctions together with small SQUID loop dimensions permits a high modulation depth of the SQUID's critical current and thus leads to very low intrinsic flux noise of the device. In particular, we present electrical characterization including detailed noise investigations. At 4.2 K, two-stage noise measurements with a SQUID as a low noise preamplifier result in a white flux noise of 51 nU 0 /Hz 1/2 , which is equivalent to an energy resolution of 1.3 h, with h being Planck's constant. Simulation of spin sensitivities results in about 1 l B /Hz 1/2 for an electron spin positioned directly above the SQUID ring. Published by AIP Publishing.

Transport and Noise Properties of sub-100-nm Planar Nb Josephson Junctions with Metallic Hf - Ti Barriers for nano-SQUID Applications

“…For fixed L = 1 pH (and d Hf-Ti = 17 nm, w eff = 250 nm, i.e., β L = 0.5), we find an optimum S 1/2 ≈ 41 n 0 / √ Hz, predicted from numerical simulation. This is in the range of lowest values achieved so far for nano-SQUIDs at 4.2 K [9,14,21].…”

“…The latter feature is in contrast to other conventional overdamped junctions, like Dayem bridges (see, e.g., Ref. [19]), small superconductor-insulator-superconductor (SIS) [20] or intrinsically shunted SNIS JJs [21], which typically have V c of the order of 100 μV. However, SNS junctions combine a number of crucial advantages, making them suitable for the realization of nano-SQUIDs.…”

Microwave Inductive Readout of EBL Nanobridge SQUIDs

“…evelopments in quantum technologies are driving the need to explore and improve the limits of macroscopic quantum superconducting devices such as SQUIDs, already capable of detecting and measuring a wide range of physical parameters, with unequalled sensitivity [1][2][3][4][5][6][7]. We are fabricating novel SQUIDs to pursue further improvement, particularly for spinflip detection.…”

Investigation of Dayem Bridge NanoSQUIDs Made by Xe Focused Ion Beam

“…S UPERCONDUCTING QUantum Interference Devices (SQUIDs) are macroscopic quantum devices that are capable of detecting and measuring a wide range of physical parameters with unequalled sensitivity [1], [2]. In addition to conventional trilayer SQUIDs whose performance has shown rapid improvements recently [3], [4], SQUIDs based on nanobridge Josephson junctions (also known as Dayem bridges) have returned to popularity in recent years, with the realization that their low capacitance and high critical current density can provide advantages of low intrinsic noise and potentially high-frequency operation [5]- [8]. In addition, their small scale in all three dimensions makes them particularly suitable for nanoSQUIDs [9]- [14].…”