The running of the Universe and the quantum structure of time

Wheeler-DeWitt equation rejects quantum effects of grown-up universes as a candidate for dark energy

In this paper, we study the changes of quantum effects of a growing universe by using Wheeler-DeWitt equation (WDWE) together with de Broglie-Bohm quantum trajectory approach. From WDWE, we obtain the quantum modified Friedmann equations which have additional terms called quantum potential compared to standard Friedmann equations. The quantum potential governs the behavior of the early universe, providing energy for inflation, while it decreases rapidly as the universe grows. The quantum potential of the grown-up universe is much smaller than that required for accelerating expansion. This indi…

Quantum-gravitational running/reduction of space-time dimension

Quantum-gravity renders the space-time dimension to depend on the size of region; it monotonically increases with the size of region and asymptotically approaches four for large distances. This effect was discovered in numerical simulations of lattice quantum gravity in the framework of causal dynamical triangulation [hep-th/0505113] as well as in renormalization group approach to quantum gravity [hep-th/0508202]. However, along these approaches the interpretation and the physical meaning of the effective change of dimension at shorter scales is not clear. Without invoking particular models in…

Free-Running Long-Distance Reference-Frame-Independent Quantum Key Distribution

Rapidly and randomly drifted reference frames will shorten the link distance and decrease the secure key rate of realistic quantum key distribution (QKD) systems. However, an actively or inappropriately implemented calibration scheme will increase complexity of the systems and may open security loopholes. In this article, we present a free-running reference-frame-independent (RFI) QKD scheme, where measurement events are classified into multiple slices with the same misalignment variation of reference frames and each slice performs the post-processing procedure individually. We perform the fre…

Non-Adiabatic Quantum Dynamics of Grover's Adiabatic Search Algorithm

We study quantum dynamics of Grover's adiabatic search algorithm with the equivalent two-level system. Its adiabatic and non-adiabatic evolutions are visualized as trajectories of Bloch vectors on a Bloch sphere. We find the change in the non-adiabatic transition probability from exponential decay for short running time to inverse-square decay for long running time. The size dependence of the critical running time is expressed in terms of Lambert $W$ function. The transitionless driving Hamiltonian is obtained to make a quantum state follow the adiabatic path. We demonstrate that a constant Ha…

Strategies for the Determination of the Running Coupling of $(2+1)$-dimensional QED with Quantum Computing

We propose to utilize NISQ-era quantum devices to compute short distance quantities in $(2+1)$-dimensional QED and to combine them with large volume Monte Carlo simulations and perturbation theory. On the quantum computing side, we perform a calculation of the mass gap in the small and intermediate regime, demonstrating, in the latter case, that it can be resolved reliably. The so obtained mass gap can be used to match corresponding results from Monte Carlo simulations, which can be used eventually to set the physical scale. In this paper we provide the setup for the quantum computation and sh…

高速率无参考框架依赖的测量设备无关量子密钥分发 with 分类蒸馏

High-Rate Free-Running Reference-Frame-Independent Measurement-Device-Independent Quantum Key Distribution with Classified Distillation

本文提出了一种在快速参考框架变化下保持高密钥率的RFI-MDI-QKD协议，通过分类蒸馏方法实现安全密钥提取，密钥率超过以往最佳方案九倍，适用于移动平台如卫星到地面链路。

Running the Dual-PQC GAN on noisy simulators and real quantum hardware

In an earlier work, we introduced dual-Parameterized Quantum Circuit (PQC) Generative Adversarial Networks (GAN), an advanced prototype of a quantum GAN. We applied the model on a realistic High-Energy Physics (HEP) use case: the exact theoretical simulation of a calorimeter response with a reduced problem size. This paper explores the dual- PQC GAN for a more practical usage by testing its performance in the presence of different types of quantum noise, which are the major obstacles to overcome for successful deployment using near-term quantum devices. The results propose the possibility of r…

Quantum creation of a universe-antiuniverse pair

If one analyses the quantum creation of the universe, it turns out that the most natural way in which the universes can be created is in pairs of universes whose time flow is reversely related. It means that the matter that propagates in one of the universes can be seen, from the point of view of the other universe, as antimatter, and viceversa. They thus form a universe-antiuniverse pair. From a global point of view, i.e. from the point of view of the whole multiverse ensemble, the creation of universes in universe-antiuniverse pairs restores the matter-antimatter asymmetry observed in each i…

Universe as quantum computer

This paper shows that universal quantum computers possess decoherent histories in which complex adaptive systems evolve with high probability.

Exponential-time quantum algorithms for graph coloring problems

The fastest known classical algorithm deciding the $k$-colorability of $n$-vertex graph requires running time $Ω(2^n)$ for $k\ge 5$. In this work, we present an exponential-space quantum algorithm computing the chromatic number with running time $O(1.9140^n)$ using quantum random access memory (QRAM). Our approach is based on Ambainis et al's quantum dynamic programming with applications of Grover's search to branching algorithms. We also present a polynomial-space quantum algorithm not using QRAM for the graph $20$-coloring problem with running time $O(1.9575^n)$. In the polynomial-space quan…

利用蒙特卡洛和量子计算方法测定(2+1)维量子电动力学跑动耦合常数

Towards determining the (2+1)-dimensional Quantum Electrodynamics running coupling with Monte Carlo and quantum computing methods

提出融合蒙特卡洛模拟与量子计算的阶梯标度策略，测定(2+1)维紧致U(1)理论的跑动耦合与非微扰Λ参数，并验证量子电路可捕捉规范物理。

A Bi-Directional Big Bang / Crunch Universe within a Two-State-Vector Quantum Mechanics?

A two boundary quantum mechanics incorporating a big bang / big crunch universe is carefully considered. After a short motivation of the concept we address the central question how a proposed a-causal quantum universe can be consistent with what is known about macroscopia and how it might find experimental support.

Lackadaisical quantum walks on triangular and honeycomb 2D grids

In the typical model, a discrete-time coined quantum walk search has the same running time of $O(\sqrt{N} \log{N})$ for 2D rectangular, triangular and honeycomb grids. It is known that for 2D rectangular grid the running time can be improved to $O(\sqrt{N \log{N}})$ using several different techniques. One of such techniques is adding a self-loop of weight $4/N$ to each vertex (i.e. making the walk lackadaisical). In this paper we apply lackadaisical approach to quantum walk search on triangular and honeycomb 2D grids. We show that for both types of grids adding a self-loop of weight $6/N$ and …