Squeezed Light and Qumodes...

Image Source: Technology Review

Topics: Computer Science, Modern Physics, Quantum Computer, Quantum Mechanics

TECHNOLOGY REVIEW: The world’s fastest computer is the Tianhe-2 supercomputer at National Super Computer Center in Guangzhou, China. It consists of 16,000 computer nodes, each with two Intel Ivy Bridge Xeon processors and three Xeon Phi coprocessor. Together these make it capable of 33.86 quadrillion floating point calculations per second, more than any other computing machine on the planet.

Clearly, the resources available to carry out a calculation are the crucial factor in its performance, and the number of calculations per second is a good guide to a computer’s power.

But quantifying the power of a quantum computer is much harder. These computing devices can perform calculations that are beyond the ken of ordinary processing machines. And yet the resources they require to do this trick are poorly understood.

Abstract

Although quantum computers are capable of solving problems like factoring exponentially faster than the best-known classical algorithms, determining the resources responsible for their computational power remains unclear. An important class of problems where quantum computers possess an advantage is phase estimation, which includes applications like factoring. We introduce a new computational model based on a single squeezed state resource that can perform phase estimation, which we call the power of one qumode. This model is inspired by an interesting computational model known as deterministic quantum computing with one quantum bit (DQC1). Using the power of one qumode, we identify that the amount of squeezing is sufficient to quantify the resource requirements of different computational problems based on phase estimation. In particular, it establishes a quantitative relationship between the resources required for factoring and DQC1. For example, we find the squeezing required to factor has an exponential scaling whereas no squeezing (i.e., a coherent state) is already sufficient to solve the hardest problem in DQC1.

Physics arXiv: The power of one qumode
Nana Liu, Jayne Thompson, Christian Weedbrook, Seth Lloyd, Vlatko Vedral, Mile Gu, Kavan Modi