2 research outputs found
Quantum Superposition States: Spin Glasses and Entanglement
Spin-glass (SG) is a fascinating system that has garnered significant
attention due to its intriguing properties and implications for various
research fields. One of the key characteristics of spin glasses is that they
contain random disorder, which leads to many possible states of the system
occurring with very close probabilities. We explore the concept of spin-glass
superposition states (SSs), which are equiprobable SSs of possible electronic
configurations. Using the Edward-Anderson (EA) type SG order parameter
and magnetization, we demonstrate that these SSs can be classified based on
their contribution to distinguishing magnetic order (disorder), such as SG,
(anti)ferromagnetic (FM), and paramagnetic (PM) phases. We also generalize
these superposition states based on the system size and investigate the
entanglement of these phase-based SSs using the negativity measure. We show
that the SG order parameter can be utilized to determine the entanglement of
magnetically ordered (disordered) phases, or vice versa, with negativity
signifying magnetic order. Our findings provide further insight into the nature
of quantum SSs and their relevance to SGs and quantum magnets. They have
implications for various fields, including condensed matter physics, where SGs
are a prototypical example of disordered systems. They are also relevant for
other fields, such as neural networks, optimization problems, and information
storage, where complex systems with random disorder behavior are greatly
interested. Overall, our study provides a deeper understanding of the behavior
of SGs and the nature of quantum SSs, with potential applications in various
fields.Comment: 8 pages, 5 figure
A Quantum Otto Engine with Shortcuts to Thermalization and Adiabaticity
We investigate the energetic advantage of accelerating a quantum harmonic
oscillator Otto engine by use of shortcuts to adiabaticity (for the power and
compression strokes) and to equilibrium (for the hot isochore), by means of
counter-diabatic (CD) driving. By comparing various protocols with and without
CD driving, we find that, applying both type of shortcuts leads to enhanced
power and efficiency even after the driving costs are taken into account. The
hybrid protocol not only retains its advantage in the limit cycle, but also
recovers engine functionality (i.e., a positive power output) in parameter
regimes where an uncontrolled, finite-time Otto cycle fails. We show that
controlling three strokes of the cycle leads to an overall improvement of the
performance metrics compared with controlling only the two adiabatic strokes.
Moreover, we numerically calculate the limit cycle behavior of the engine and
show that the engines with accelerated isochoric and adiabatic strokes display
a superior power output in this mode of operation.Comment: 12 pages, 7 figure