Ultra-low-noise magnetic sensing with long Josephson tunnel junctions (original) (raw)

Josephson Directional Amplifier for Quantum Measurement of Superconducting Circuits

Physical Review Letters, 2014

We realize a microwave quantum-limited amplifier that is directional and can therefore function without the front circulator needed in many quantum measurements. The amplification takes place in only one direction between the input and output ports. Directionality is achieved by multipump parametric amplification combined with wave interference. We have verified the device noise performances by using it to read out a superconducting qubit and observed quantum jumps. With an improved version of this device, the qubit and preamplifer could be integrated on the same chip.

Ultrasensitive proximity Josephson sensor with kinetic inductance readout

Applied Physics Letters, 2008

We propose a mesoscopic kinetic-inductance radiation detector based on a long superconductornormal metal-superconductor Josephson junction. The operation of this proximity Josephson sensor (PJS) relies on large kinetic inductance variations under irradiation due to the exponential temperature dependence of the critical current. Coupled with a dc SQUID readout, the PJS is able to provide a signal to noise (S/N) ratio up to ∼ 10 3 in the THz regime if operated as calorimeter, while electrical noise equivalent power (NEP) as low as ∼ 7 × 10 −20 W/ √ Hz at 200 mK can be achieved in the bolometer operation. The high performance together with the ease of fabrication make this structure attractive as an ultrasensitive cryogenic detector of THz electromagnetic radiation. PACS numbers: 85.25.Oj,74.45.+c,73.50.Lw Superconducting single-photon detectors [1, 2, 3] offer high infrared detection efficiency, high-speed timing resolution and few-nanosecond reset times. They have been applied in several fields including spectroscopy of ultrafast quantum phenomena [4], optical communications [5], quantum cryptography [6], and fast digital circuit testing . On the other hand, a wide potential for superconducting nanoscale detectors used as advanced bolometers is also expected in several astrophysical space applications, where bolometers are promising candidates to meet future needs of cooled telescopes. The interest lies in the negligible Johnson noise they show with a NEP as low as 10 −18 W/ √ Hz. Hot-electron resistive microbolometers and kinetic inductance superconducting detectors (KIDs) represent high performance devices able to reach NEP 10 −19 W/ √ Hz at T ≥ 1 K [8]. KIDs [9] offer about the same NEP and response time as resistive bolometers and hot electron detectors, and they can operate at temperatures much below the critical temperature where the generation-recombination noise is small thanks to the reduced number of quasiparticles.

Achievements and potential of the Josephson effect in new superconducting devices

Physica B: Condensed Matter, 2002

Since many years, superconductive tunnel junction devices have been widely investigated in the context of energy spectroscopy. High-resolution detectors for energy spectroscopy have been realized based on the single particle tunneling. On the other hand, the Josephson effect offers a very powerful tool for the design of proper detector configurations and an intrinsic potential for fast-response detectors to the radiation interaction. The present paper deals with this last issue discussing the underlying physical aspects and potential performance of such devices. r (A. Barone). 0921-4526/02/$ -see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 -4 5 2 6 ( 0 2 ) 0 0 8 5 7 -8

Mesoscopic superconducting tunnel junction devices : experimental studies of performance limitations

2005

In this work four different mesoscopic superconducting devices have been experimentally studied: an ammeter based on a hysteretic Josephson junction switching from the superconducting state to the normal state, a conventional Cooper pair pump (CPP) based on two superconducting islands separated by tunnel junctions, a novel flux assisted Cooper pair pump and a thermometer based on a tunnel junction between a superconductor and a normal metal. These devices make use of phenomena related to superconductivity and are also benefiting from some properties of small structures, e.g., of quantum mechanical tunneling and of transport of single electrons. The present research focused on investigating performance limitations of these devices and the aim was to improve their performance. A hysteretic Josephson junction switching can be used as a sensitive current threshold detector. For many purposes, a smaller critical current I_c of the detecting junction would yield a higher current sensitivity. It was found in this Thesis that the main limitation of the ammeter is that with increasing sensitivity the negative effects due to dissipation start to dominate. In this Thesis the Josephson junction was also demonstrated as a shot-noise detector, and it was concluded that this kind of a device could probably be made into an absolute on-chip detector of Fano-factors and noise in general. A charge pump is a device which can periodically transfer a discrete amount of charge Q through an electrical circuit. The measured double island CPP introduced a frequency dependent current with a value close to the expected one at low pumping frequencies. The drawback in the measurements was that the direction of the pumped current was set by the bias voltage. The results of the measurement on flux assisted pumping were indeed very promising and the studied device was able to produce sufficiently high pumped currents of around 0.1 nA with reasonable accuracy. Thermometer based on NIS (Normal metal-Insulator-Superconductor) tunnel junctions is a very promising temperature sensor for bolometric radiation sensor applications. This work showed that it can be used as a sensitive thermometer up to MHz frequencies range and that its response time is limited by the electron-phonon scattering rate. Josephson junction, phase diffusion, Cooper pair pump, NIS tunnel junction 165 951-22-7709-3

Low-field magnetic response of multi-junction superconducting quantum interference devices

The European Physical Journal B, 2008

The magnetic states of multi-junction superconducting quantum interference device containing 2N identical conventional Josephson junctions are studied by means of a perturbation analysis of the non-linear first-order ordinary differential equations governing the dynamics of the Josephson junctions in these devices. In the zero-voltage state, persistent currents are calculated in terms of the externally applied magnetic flux Φex. The resulting d.c. susceptibility curves show that paramagnetic and diamagnetic states are present, depending on the value of Φex. The stability of these states is qualitatively studied by means of the effective potential notion for the system.

Flicker (1∕f) noise in the critical current of Josephson junctions at 0.09–4.2 K

Applied Physics Letters, 2004

We have measured the low-frequency noise in the critical current I c of six dc superconducting quantum interference devices (SQUIDs) with resistively shunted Nb-NbO x -PbIn Josephson junctions in the temperature range T = 0.09-4.2 K. Each device is voltage biased, the applied flux is an integer number of flux quanta, and the current fluctuations are measured with a second dc SQUID. At low frequencies f, there is a component of the power spectrum of the critical current fluctuations given approximately by S I c ͑f͒ = CI c 2 T 2 / Af, where A is the area of both junctions, and C Ϸ͑3.9± 0.4͒ ϫ 10 −23 m 2 /K 2 . For quantum bits based on Josephson junctions, the scaling of S I c ͑f͒ with T 2 implies that the dephasing time limited by critical current l / f noise should scale as 1 / T for temperatures down to at least 0.09 K.

High-Tc superconducting detector for highly-sensitive microwave magnetometry

Applied Physics Letters

We have fabricated arrays of High-T c Superconducting Quantum Interference Devices (SQUIDs) with randomly distributed loop sizes as sensitive detectors for Radio Frequency (RF) waves. These subwavelength size devices known as Superconducting Quantum Interference Filters (SQIFs) detect the magnetic component of the electromagnetic field. We used a scalable ion irradiation technique to pattern the circuits and engineer the Josephson junctions needed to make SQUIDs. Here, we report on a 300 SQUID series array with the loop area ranging from 6 to 60 lm 2 , folded in a meander line covering a 3.5 mm  120 lm substrate area, made out of a 150 nm thick YBa 2 Cu 3 O 7 film. Operating at a temperature of T ¼ 66 K in an unshielded magnetic environment under low DC bias current (I ¼ 60 lA) and a DC magnetic field (B ¼ 3 lT), this SQIF can detect a magnetic field of a few picoteslas at a frequency of 1.125 GHz, which corresponds to a sensitivity of a few hundreds of fT= ffiffiffiffiffiffi Hz p and shows a linear response over 7 decades in RF power. This work is a promising approach for the realization of low dissipative subwavelength gigahertz magnetometers.