Exploring out-of-equilibrium quantum magnetism and thermalization in a spin-3 many-body dipolar lattice system

Understanding quantum thermalization through entanglement build-up in isolated quantum systems addresses fundamental questions on how unitary dynamics connects to statistical physics. Here, we study the spin dynamics and approach towards local thermal equilibrium of a macroscopic ensemble of S = 3 spins prepared in a pure coherent spin state, tilted compared to the magnetic field, under the effect of magnetic dipole-dipole interactions. The experiment uses a unit filled array of 104 chromium atoms in a three dimensional optical lattice, realizing the spin-3 XXZ Heisenberg model. The buildup of quantum correlation during the dynamics, especially as the angle approaches pi/2, is supported by comparison with an improved numerical quantum phase-space method and further confirmed by the observation that our isolated system thermalizes under its own dynamics, reaching a steady state consistent with the one extracted from a thermal ensemble with a temperature dictated from the system's energy. This indicates a scenario of quantum thermalization which is tied to the growth of entanglement entropy. Although direct experimental measurements of the Renyi entropy in our macroscopic system are unfeasible, the excellent agreement with the theory, which can compute this entropy, does indicate entanglement build-up.Comment: 12 figure

Engineering of microfabricated ion traps and integration of advanced on-chip features

Atomic ions trapped in electromagnetic potentials have long been used for fundamental studies in quantum physics. Over the past two decades, trapped ions have been successfully used to implement technologies such as quantum computing, quantum simulation, atomic clocks, mass spectrometers and quantum sensors. Advanced fabrication techniques, taken from other established or emerging disciplines, are used to create new, reliable ion-trap devices aimed at large-scale integration and compatibility with commercial fabrication. This Technical Review covers the fundamentals of ion trapping before discussing the design of ion traps for the aforementioned applications. We overview the current microfabrication techniques and the various considerations behind the choice of materials and processes. Finally, we discuss current efforts to include advanced, on-chip features in next-generation ion traps

Direct democracy and the constitution

This chapter applies a comparative view to evaluate initiatives and referendums in the context of Constitutional change. Instruments of direct democratic decision making are compared to those of a purely representative democratic system in which members of parliament decide Constitutional issues like basic rights, the scope of democratic decision making and market exchange, the organization of government and the judiciary, and the federal structure of the country. Section 2 briefly describes aspects of direct democratic decision making that we deem critical from a Constitutional economics perspective. In particular, we hint to changes in the political process if citizens are directly involved through initiatives and referendums

Room-temperature cavity quantum electrodynamics with strongly coupled Dicke states

Quantum Engineering: ambient solid-state quantum optics Creating practical solid-state, quantum computers that operate at room-temperature is a challenging task. This is because stored information is readily destroyed by thermal noise. A signature of a physical system’s ability to function as a quantum computer is the observation of quantum Rabi oscillations since they represent the possibility of “reading” and “writing” quantum information. Thus far, these have been observed reliably and consistently only at milli-Kelvin temperatures. Jonathan Breeze at Imperial College London and collaborators have used an organic molecular crystal, a dielectric resonator and pulses of laser light to produce pronounced quantum Rabi oscillations at microwave frequencies, lasting up to 10 microseconds at room-temperature. This discovery paves the way for room-temperature quantum information processing devices such as spin memories and quantum-enhanced technologies for metrology, sensing, communications and ultimately – quantum computing

Room-temperature cavity quantum electrodynamics with strongly-coupled Dicke states

The strong coupling regime is essential for efficient transfer of excitations between states in different quantum systems on timescales shorter than their lifetimes. The coupling of single spins to microwave photons is very weak but can be enhanced by increasing the local density of states by reducing the magnetic mode volume of the cavity. In practice, it is difficult to achieve both small cavity mode volume and low cavity decay rate, so superconducting metals are often employed at cryogenic temperatures. For an ensembles of N spins, the spin–photon coupling can be enhanced by N−−√N through collective spin excitations known as Dicke states. For sufficiently large N the collective spin–photon coupling can exceed both the spin decoherence and cavity decay rates, making the strong-coupling regime accessible. Here we demonstrate strong coupling and cavity quantum electrodynamics in a solid-state system at room-temperature. We generate an inverted spin-ensemble with N ~ 1015 by photo-exciting pentacene molecules into spin-triplet states with spin dephasing time T∗2~3T2*~3 μs. When coupled to a 1.45 GHz TE01δ mode supported by a high Purcell factor strontium titanate dielectric cavity (Vm~0.25Vm~0.25 cm3, Q ~ 8,500), we observe Rabi oscillations in the microwave emission from collective Dicke states and a 1.8 MHz normal-mode splitting of the resultant collective spin–photon polariton. We also observe a cavity protection effect at the onset of the strong-coupling regime which decreases the polariton decay rate as the collective coupling increases

Water quality degradation of coastal waterways in the Wet Tropics, Australia

The Wet Tropics region of north Queensland has outstanding environmental values, contains the highest biological diversity in Australia, and borders the Great Barrier Reef. Comparable to other tropical areas worldwide, increasing urban and agricultural development in the Wet Tropics has caused concerns with respect to ecosystem degradation due to poor water quality in freshwater reaches and marine environments. Key issues currently identified in the Wet Tropics include erosion and subsequent stream turbidity and sedimentation, nutrients from erosion and fertiliser use and pesticide residue contamination. Issues such as reduced dissolved oxygen, acid sulfate soil runoff, and biological factors such as weed infestation, reduced and degraded riparian vegetation condition, and flow modification have also been identified. These issues mainly arise from agricultural activities with lesser effects from urban development. Management of pollution to improve in-stream water quality requires a long-term monitoring program to characterize water quality conditions over different flows and seasons. This type of monitoring program is underway; however, the focus is on the Great Barrier Reef and does not fully consider freshwater ecosystem health. Another major issue is the lack of a fully developed conceptual framework that links changed land use to water quality and subsequently to aquatic ecosystem health. In this paper, we establish the current level of water quality knowledge in the Wet Tropics while outlining a conceptual framework connecting changing land management practices and their effects to water quality and to ecosystem health