2,444 research outputs found
Phase-Tunable Thermal Logic: Computation with Heat
Boolean algebra, the branch of mathematics where variables can assume only
true or false value, is the theoretical basis of classical computation. The
analogy between Boolean operations and electronic switching circuits,
highlighted by Shannon in 1938, paved the way to modern computation based on
electronic devices. The grow of computational power of such devices, after an
exciting exponential -Moore trend, is nowadays blocked by heat dissipation due
to computational tasks, very demanding after the chips miniaturization. Heat is
often a detrimental form of energy which increases the systems entropy
decreasing the efficiency of logic operations. Here, we propose a physical
system able to perform thermal logic operations by reversing the old
heat-disorder epitome into a novel heat-order paradigm. We lay the foundations
of heat computation by encoding logic state variables in temperature and
introducing the thermal counterparts of electronic logic gates. Exploiting
quantum effects in thermally biased Josephson junctions (JJs), we propound a
possible realization of a functionally complete dissipationless logic. Our
architecture ensures high operation stability and robustness with switching
frequencies reaching the GHz
Phase-Tunable Temperature Amplifier
Coherent caloritronics, the thermal counterpart of coherent electronics, has
drawn growing attention since the discovery of heat interference in 2012.
Thermal interferometers, diodes, transistors and nano-valves have been
theoretically proposed and experimentally demonstrated by exploiting the
quantum phase difference between two superconductors coupled through a
Josephson junction. So far, the quantum-phase modulator has been realized in
the form of a superconducting quantum interference device (SQUID) or a
superconducting quantum interference proximity transistor (SQUIPT). Thence, an
external magnetic field is necessary in order to manipulate the heat transport.
Here, we theoretically propose the first on-chip fully thermal caloritronic
device: the phase-tunable temperature amplifier. Taking advantage of a recent
thermoelectric effect discovered in spin-split superconductors coupled to a
spin-polarized system, by a temperature gradient we generate the magnetic flux
controlling the transport through a temperature biased SQUIPT. By employing
commonly used materials and a geometry compatible with state-of-the-art
nano-fabrication techniques, we simulate the behavior of the temperature
amplifier and define a number of figures of merit in full analogy with voltage
amplifiers. Notably, our architecture ensures infinite input thermal impedance,
maximum gain of about 11 and efficiency reaching the 95%. This device concept
could represent a breakthrough in coherent caloritronic devices, and paves the
way for applications in radiation sensing, thermal logics and quantum
information.Comment: 7 pages, 3 figure
Phase-tunable Josephson thermal router
Since the the first studies of thermodynamics, heat transport has been a
crucial element for the understanding of any thermal system. Quantum mechanics
has introduced new appealing ingredients for the manipulation of heat currents,
such as the long-range coherence of the superconducting condensate. The latter
has been exploited by phase-coherent caloritronics, a young field of
nanoscience, to realize Josephson heat interferometers, which can control
electronic thermal currents as a function of the external magnetic flux. So
far, only one output temperature has been modulated, while multi-terminal
devices that allow to distribute the heat flux among different reservoirs are
still missing. Here, we report the experimental realization of a phase-tunable
thermal router able to control the heat transferred between two terminals
residing at different temperatures. Thanks to the Josephson effect, our
structure allows to regulate the thermal gradient between the output electrodes
until reaching its inversion. Together with interferometers, heat diodes and
thermal memories, the thermal router represents a fundamental step towards the
thermal conversion of non-linear electronic devices, and the realization of
caloritronic logic components.Comment: 9 pages, 5 figure
A gate- and flux-controlled supercurrent diode
Non-reciprocal charge transport in supercurrent diodes (SDs) polarized
growing interest in the last few years for its potential applications in
superconducting electronics (SCE). So far, SD effects have been reported in
complex hybrid superconductor/semiconductor structures or metallic systems
subject to moderate magnetic fields, thus showing a limited potentiality for
practical applications in SCE. Here, we report the design and the realization
of a monolithic SD by exploiting a Dayem bridge-based superconducting quantum
interference device (SQUID). Our structure allows reaching rectification
efficiencies () up to about 6%. Moreover, the absolute value and the
polarity of can be selected on demand by the modulation of an external
magnetic flux or by a gate voltage, thereby guaranteeing high versatility and
improved switching speed. Furthermore, our SD operates in a wide range of
temperatures up to about the 70% of the superconducting critical temperature of
the titanium film composing the interferometer. Our SD can find extended
applications in SCE by operating in synergy with widespread superconducting
technologies, such as nanocryotrons, rapid single flux quanta (RSFQs) and
memories.Comment: 5 pages, 4 figure
Preliminary demonstration of a persistent Josephson phase-slip memory cell with topological protection
Superconducting computing promises enhanced computational power in both classical and quantum approaches. Yet, scalable and fast superconducting memories are not implemented. Here, we propose a fully superconducting memory cell based on the hysteretic phase-slip transition existing in long aluminum nanowire Josephson junctions. Embraced by a superconducting ring, the memory cell codifies the logic state in the direction of the circulating persistent current, as commonly defined in flux-based superconducting memories. But, unlike the latter, the hysteresis here is a consequence of the phase-slip occurring in the long weak link and associated to the topological transition of its superconducting gap. This disentangles our memory scheme from the large-inductance constraint, thus enabling its miniaturization. Moreover, the strong activation energy for phase-slip nucleation provides a robust topological protection against stochastic phase-slips and magnetic-flux noise. These properties make the Josephson phase-slip memory a promising solution for advanced superconducting classical logic architectures or flux qubits
Thermal superconducting quantum interference proximity transistor
Superconductors are known to be excellent thermal insulators at low
temperature owing to the presence of the energy gap in their density of states
(DOS). In this context, the superconducting \textit{proximity effect} allows to
tune the local DOS of a metallic wire by controlling the phase bias ()
imposed across it. As a result, the wire thermal conductance can be tuned over
several orders of magnitude by phase manipulation. Despite strong implications
in nanoscale heat management, experimental proofs of phase-driven control of
thermal transport in superconducting proximitized nanostructures are still very
limited. Here, we report the experimental demonstration of efficient heat
current control by phase tuning the superconducting proximity effect. This is
achieved by exploiting the magnetic flux-driven manipulation of the DOS of a
quasi one-dimensional aluminum nanowire forming a weal-link embedded in a
superconducting ring. Our thermal superconducting quantum interference
transistor (T-SQUIPT) shows temperature modulations up to mK yielding
a temperature-to-flux transfer function as large as mK/. Yet,
phase-slip transitions occurring in the nanowire Josephson junction induce a
hysteretic dependence of its local DOS on the direction of the applied magnetic
field. Thus, we also prove the operation of the T-SQUIPT as a phase-tunable
\textit{thermal memory}, where the information is encoded in the temperature of
the metallic mesoscopic island. Besides their relevance in quantum physics, our
results are pivotal for the design of innovative coherent caloritronics devices
such as heat valves and temperature amplifiers suitable for thermal logic
architectures.Comment: 8 pages, 4 figure
Thermoelectric single-photon detection through superconducting tunnel junctions
Bipolar thermoelectricity in tunnel junctions between superconductors of
different energy gap has been recently predicted and experimentally
demonstrated. This effect showed thermovoltages up to V at
milliKelvin temperatures. Thus, superconducting tunnel junctions can be
exploited to realize a passive single-photon thermoelectric detector
operating in the broadband range 15 GHz - 50 PHz. In particular, this detector
is expected to show a signal-to-noise ratio of about 15 down to GHz
and a operating window of more than 4 decades. Therefore, the might find
applications in quantum computing, telecommunications, optoelectronics,
spectroscopy and astro-particle physics.Comment: 7 pages, 3 figure
Corrigendum to a new neurocognitive interpretation of shoulder position sense during reaching:unexpected competence in the measurement of extracorporeal space
[This corrects the article DOI: 10.1155/2016/9065495.
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