Projects

Principle Investigator: Ali Bozbey, TOBB ETU
Supported by: TUBITAK – ANR
Project Dates: 2018-2020

Ultrasensitive magnetometry is required in various applications and superconducting quantum interference devices (SQUIDs) are known as the most sensitive magnetic field sensors and are widely used in all fields requiring ultimate sensitivities such as solid-state physics, biomagnetism, medicine with magnetoencephalography and magnetocardiography, archeology, earthquake detection, subsoil sounding for hydrogeology and environmental purposes, nondestructive evaluation, radiation detector dead-out and even quantum bit read-out applications. So far, analog Superconducting Quantum Interference Devices (SQUIDs) have successfully met stringent requirements for such uses, with a sensitivity level today reaching less than 1fT/ÖHz for cm-sized sensors and a few tens of nΦ₀/ÖHz for nanometer size. Here Φ₀=h/2e is the quantum of magnetic flux. Depending on the target application, SQUIDs can work in a magnetic shielded environment or must operate in unshielded conditions.

Important parameters that characterize SQUID systems are their sensitivity and their magnetic flux to voltage transfer characteristics. The state-of-the-art magnetic field sensitivity is of the order of a few fT/ÖHz for low-Tc SQUIDs and below 40 fT/ÖHz for their high-Tc counterparts, corresponding roughly to flux sensitivities in the range of a few µF₀/ÖHz for signals around the 1 Hz frequency range. The standard configuration is to operate the nonlinear SQUID in feedback mode with a flux-locked loop. When outdoor measurements need to be done, for instance, for archeology or geophysical applications, then magnetically unshielded devices are required. This puts a strong constraint on the dynamic range of the device, taken between the noise floor of the device and its maximum output amplitude level. The dynamic range can also be the maximum signal-to-noise ratio (SNR), measured in amplitude and not in power unit, that the sensor can achieve without distortion of the signal. Indeed, it has to detect fields in the femtotesla range while being moved in the earth’s magnetic field with an amplitude of around 50 µT.  In this project, we aim to tackle these points and develop a fully monolithic digital SQUID without any room temperature processing electronics and increase the sensitivities of the digital SQUID to levels suitable for using in geophysical applications.

Principle Investigator: Ali Bozbey, TOBB ETU
Supported by: TUBITAK – COST
Project Dates: 2018-2021

There are reports and preliminary data that show that there is some relationship between the seismic events and the fluctuations of the magnetic field of the Earth. There are more than 50 countries possessing stations to monitor these fluctuations, which are being researched to be used as earthquake precursors. The biggest obstacle for the success of this research is that current magnetic field measurement systems do not have sufficient sensitivity. Other important obstacles include a lack of registered data and the intrinsic complexity of underlying physical mechanisms. In addition, the magnetic field is also affected by plenty of phenomena and discrimination of their origin is not so easy. Nevertheless, the magnetic signatures of miscellaneous events already observed with [SQUID]² magnetometer at the Low Noise LSBB laboratory are in favor of a more advanced set of magnetometers arranged in a network to better understand the origin and location of observed signatures.

In this project we plan to use Superconducting Quantum Interference Device – SQUID, to install one SQUID magnetic observation station in Turkey that can record with 1pT sensitivity and 500 Hz sampling frequency. Then to network the station to the already installed systems in France and South Africa. The first station is a Low Temperature Superconductor (LTS) SQUID device in the Low Background Noise Underground Laboratory (LSBB – Laboratoire Souterrain à Bas Bruit) shielded underground low noise environment in France, the second one is a High Temperature Superconductor set in a non-magnetic dedicated unshielded house located in Hermanus, South African National Space Agency. Eventually, with the interest of some groups in USA, Philippines, Japan, Argentina, and Bulgaria a network of stations can be distributed all around the world. Hence, it may be possible to extract meaningful and correlated information with the seismic events if the data from many stations are fused.

Besides, these developments will be useful for observations of other phenomena, like the ones connected to space weather or hydrogeology.

Principle Investigator: Ali Bozbey, TOBB ETU
Supported by: TUBITAK
Project Dates: 2012-2015

Rapid single flux quantum (RSFQ) is a digital and analog electronics technology for signal switching based on the quantum effects of superconducting materials. Since RSFQ circuits are based on the superconductivity, cryogenic environment is needed for their operation. The basic advantage of RSFQ over their CMOS equivalents is the switching ability at THz frequencies and low power consumption. Furthermore, RSFQ technology is compatible with standard CMOS design and production systems that the integration of RSFQ circuits with CMOS and optical based circuits is possible. RSFQ VLSI circuits have advanced quite a lot in the recent years and it has been possible to make complicated circuits.

Until sometime, while the existing design tools were more advanced than the fabrication technologies, recently the fabrication technologies are established and reliable foundries are available. Current fabrication technologies are at a level of fabricating 2.000.000 Josephson junctions with zero error. However, functional digital circuits are much smaller than this. It is anticipated that one of the reasons for this is that the existing design tools do not take into account the noise, jitter and statistical timing of the circuits.

We aim to develop a design and optimization tool that takes into account the noise, jiter and loading of the RSFQ circuits by using the simulators with stochasting modeling ability and perform the tests on the fabricated chips which are designed according to the parameters given by the developed optimization tool. By using this tool, we aim to develop a comparator circuit with the lowest gray zone width, an RSFQ library (TFF, DFF, AND, OR, JTL, NOT cells etc.) with optimized parameters and a complicated aritmetic logic unit (ALU) consisting of many Josephson junctions.