Theoretical and experimental exploration of quantum effects in superconducting electronics
Abstract
Theoretical and experimental exploration of quantum effects in superconducting electronics Superconductors, being macroscopic quantum objects, provide a fertile ground for the exploration of quantum effects. In turn, these quantum effects, being theoretically explored and experimentally confirmed, may translate into unique and potentially vitally important additions in various practical applications of superconductors in electronics. This effort will pursue 2 different kinds of quantum effects. The first type is related with a well-known phenomenon: lasing. Contemporary laser physics is realized in a large variety of objects, spanning the size scale and complexity of physics from black holes to nano-needles. Solid state lasers, including semiconductor lasers, are very widespread in our technological world and cover the whole range of electromagnetic spectrum, including terahertz-range. However, superconducting lasers have not yet been demonstrated. Having an energy-efficient, compact and co-fabricable with mixed signal and logic circuits, superconducting lasers could make a difference for some demanding applications. In particular, applying small SFQ pulse signals to cross the lasing threshold, one can hope to achieve a large output beam amplitude modulation for small dissipated power. Such a device would solve the information transfer problem from the cryogenic environment to room temperature which is a current concern for the superconducting computing and detector communities. The hardest issue is how to obtain the required population inversion, the so called “negative temperature” states in nonequilibrium superconductors. Injection of excess electron excitations or breaking the existent Cooper pairs can serve this task. However, choosing the right parameters for the materials, geometry, and biasing must be done carefully for success to result. Many parasitic absorption channels and many physical processes compet with lasing when one is in a “negative temperature” state in superconductors. This effort will use a variety of theoretical instruments to explore this parameter space and locate an optimal pathways for successful implementation. The second problem, which is proposed to be attacked experimentally, is whether or not it is possible to register locally (or quasi-locally) the so-called Aharonov-Bohm potential. This potential, which can be non-zero even in the local absence of a magnetic field, has been proven to act physically on quantum objects including superconductors. Sometimes it is described as describing action at a distance. Contrary to this, R. Feynman noticed in famous "Lectures" that "if we want to describe its (-magnetic field s) influence not as action-at-a-distance ("spukhafte Fernwirkung", as Einstein would have said), we must use the vector potential" as a real physical field. He opposed the arguments first suggested by Heaviside that the vector potential is nothing more than the mathematical tool. Interestingly, in quantum physics of charged particles the current has a term proportional to the vector potential. Since the current must be gauge invariant, while the contribution by the vector-potential is not, there are other terms which counterbalance the gauge non-invariance. These extra terms are expressed in terms of the wave-function of the charged particle. This is an obvious case when "apples" are being added to "oranges". At this point a big puzzle is noticeable: how can different constituents contribute on equal footing? In particular, the vector potential may originate externally to the volume occupied by the particle and the particle just moves under its influence. The only way to resolve this contradiction is to suppose that the particle "feels" the vector potential. A strong basis for capturing the truth through experimentation has already been prepared. Important corollaries for both quantum physics and it applications are expected to result from this work.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 09, 2016
- Source ID
- N000141612269
Entities
People
- Armen Gulian
Organizations
- Chapman University
- Office of Naval Research
- United States Navy