Phase-Preserving Linear Amplifiers Not Simulable by the Parametric Amplifier.
Physical review letters 125:16 (2020) 163603
Abstract:
It is commonly accepted that a parametric amplifier can simulate a phase-preserving linear amplifier regardless of how the latter is realized [C. M. Caves et al., Phys. Rev. A 86, 063802 (2012)PLRAAN1050-294710.1103/PhysRevA.86.063802]. If true, this reduces all phase-preserving linear amplifiers to a single familiar model. Here we disprove this claim by constructing two counterexamples. A detailed discussion of the physics of our counterexamples is provided. It is shown that a Heisenberg-picture analysis facilitates a microscopic explanation of the physics. This also resolves a question about the nature of amplifier-added noise in degenerate two-photon amplification.Coarse and fine-tuning of lasing transverse electromagnetic modes in coupled all-inorganic perovskite quantum dots
Nano Research Springer 14 (2020) 108-113
Abstract:
Inorganic perovskite lasers are of particular interest, with much recent work focusing on Fabry-Pérot cavity-forming nanowires. We demonstrate the direct observation of lasing from transverse electromagnetic (TEM) modes with a long coherence time ∼ 9.5 ps in coupled CsPbBr3 quantum dots, which dispense with an external cavity resonator and show how the wavelength of the modes can be controlled via two independent tuning-mechanisms. Controlling the pump power allowed us to fine-tune the TEM mode structure to the emission wavelength, thus providing a degree of control over the properties of the lasing signal. The temperature-tuning provided an additional degree of control over the wavelength of the lasing peak, importantly, maintained a constant full width at half maximum (FWHM) over the entire tuning range without mode-hopping.
Classical Mechanics: A professor–student collaboration
Institute of Physics Publishing (2020)
Abstract:
Classical Mechanics: A professor-student collaboration is a textbook tailored for undergraduate physics students embarking on a first-year module in Newtonian mechanics. This book was written as a unique collaboration between Professor Mario Campanelli and students that attended his course in Classical Mechanics at University College London (UCL). Taking his lecture notes as a starting point, and reflecting on their own experiences studying the material, the students worked together with Prof. Campanelli to produce a comprehensive course text that covers a familiar topic from a new perspective.
Quantum Refrigeration with Indefinite Causal Order.
Physical review letters 125:7 (2020) 070603
Abstract:
We propose a thermodynamic refrigeration cycle which uses indefinite causal orders to achieve nonclassical cooling. The cycle cools a cold reservoir while consuming purity in a control qubit. We first show that the application to an input state of two identical thermalizing channels of temperature T in an indefinite causal order can result in an output state with a temperature not equal to T. We investigate the properties of the refrigeration cycle and show that thermodynamically, the result is compatible with unitary quantum mechanics in the circuit model but could not be achieved classically. We believe that this cycle could be implemented experimentally using tabletop photonics. Our result suggests the development of a new class of thermodynamic resource theories in which operations are allowed to be performed in an indefinite causal order.Aharonov-Bohm Phase is Locally Generated Like All Other Quantum Phases.
Physical review letters 125:4 (2020) 040401