Copenhagen Computation: How I Learned to Stop Worrying and Love Bohr

Quantum searching a classical database (or how we learned to stop worrying and love the bomb)

We show how to perform a quantum search for a classical object, specifically for a classical object which performs no coherent evolution on the quantum computer being used for the search. We do so by using interaction free measurement as a subroutine in a quantum search algorithm. In addition to providing a simple example of how non-unitary processes which approximate unitary ones can be useful in a quantum algorithm, our procedure requires only one photon regardless of the size of the database, thereby establishing an upper bound on the amount of energy required to search an arbitrarily large…

Decoherence and Ontology, or: How I Learned To Stop Worrying And Love FAPP

I make the case that the Universe according to unitary (no-collapse) quantum theory has a branching structure, and so can literally be regarded as a "many-worlds" theory. These worlds are not part of the fundamental ontology of quantum theory - instead, they are to be understood as structures, or patterns, emergent from the underlying theory, through the dynamical process of decoherence. That they are structures in this sense does not mean that they are in any way unreal: indeed, pretty much all higher-level ontology in science, from tables to phonons to tigers, is likewise emergent. Unitary q…

How quickly can anyons be braided? Or: How I learned to stop worrying about diabatic errors and love the anyon

Topological phases of matter are a potential platform for the storage and processing of quantum information with intrinsic error rates that decrease exponentially with inverse temperature and with the length scales of the system, such as the distance between quasiparticles. However, it is less well-understood how error rates depend on the speed with which non-Abelian quasiparticles are braided. In general, diabatic corrections to the holonomy or Berry's matrix vanish at least inversely with the length of time for the braid, with faster decay occurring as the time-dependence is made smoother. W…

环上的一粒子或：我如何学会停止担心并爱θ-真空

A particle on a ring or: how I learned to stop worrying and love $θ$-vacua

作者批判性地检验了通过在欧几里得路径积分中先取时空体积趋于无穷大再求和所有拓扑扇区的特定顺序来避免强CP问题的提议，发现该方法无法正确重现能量谱。

我如何学会不再担忧并爱上Redfield方程：非马尔可夫动力学的完全正重求和

How I Learned to Stop Worrying and Love the Redfield Equation: Completely-Positive Resummation of Non-Markovian Dynamics

本文比较Redfield方程与Magnus重求和，证明弱耦合下非马尔可夫Redfield演化仍接近CPTP映射，并给出可靠性判据。