Quantum Scientists Break Aluminium ‘Monopoly’

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Credit: TUDelft/Tremani

Courtesy of Phys.org:

A Majorana fermion, or a Majorana particle, is a fermion that is its own antiparticle. Discovering the Majorana was the first step, but utilizing it as a quantum bit (qubit) still remains a major challenge. An important step towards this goal has just been taken by researchers from TU Delft in today’s issue of Nature Physics. It is a nearly thirty-year-old scientific problem that has just been resolved: demonstrating the difference between the even and odd occupation of a superconductor in high magnetic fields. Thus far, this was only possible in aluminium, which is incompatible with Majoranas. This result enables the read out and manipulation of quantum states encoded in prospective Majorana qubits.

Qubit

Qubits store information similarly to normal (digital) bits. While a bit represents either 0 or 1, a qubit utilizes the laws of quantum mechanics, making it possible to be in a superstate of 0 and 1 simultaneously. This enables solving several mathematical problems much faster than the most capable supercomputers ever built. Several research groups and companies around the globe are pursuing the development and prototyping of such a powerful quantum computer, including QuTech at the Delft University of Technology in The Netherlands.

Majoranas

A qubit encoded by Majorana’s is a promising building block for a practical quantum computer. Until now, it was a major challenge to read out such a Majorana qubit. In order to do so, one needs to determine whether the number of the electrons is even or odd, or, in other words, what the parity state is. The measurement of the parity of superconductors has been performed for the last thirty years, however, successful experiments were exclusively done on aluminium while all attempts addressing different superconducting materials, such as vanadium or niobium, have failed. This is a major issue for Majorana research as superconductivity is required to survive in high magnetic fields, at which aluminium ceases to be a superconductor. Continue reading

Scientists Report Finding Reliable Way to Teleport Data

Courtesy of The New York Times:

Scientists in the Netherlands have moved a step closer to overriding one of Albert Einstein’s most famous objections to the implications of quantum mechanics, which he described as “spooky action at a distance.”

In a paper published on Thursday in the journal Science, physicists at the Kavli Institute of Nanoscience at the Delft University of Technology reported that they were able to reliably teleport information between two quantum bits separated by three meters, or about 10 feet.

Quantum teleportation is not the “Star Trek”-style movement of people or things; rather, it involves transferring so-called quantum information — in this case what is known as the spin state of an electron — from one place to another without moving the physical matter to which the information is attached.

Classical bits, the basic units of information in computing, can have only one of two values — either 0 or 1. But quantum bits, or qubits, can simultaneously describe many values. They hold out both the possibility of a new generation of faster computing systems and the ability to create completely secure communication networks.

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A forest of optical elements that was part of the quantum teleportation device used by the team of physicists in the Netherlands. Credit Hanson lab@TUDelft

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The Development of Quantum Mechanics

Courtesy of Upscale:

Introduction

Working essentially independently, in the mid-1920’s Heisenberg and Schrödinger both created a full form of Quantum Mechanics. How these two extraordinary events occurred has been extensively studied; a favorite reference is Max Jammer, The Conceptual Development of Quantum Mechanics (McGraw-Hill 1966).

Here we briefly outline some of the key features of these developments. Some of the material is well-known, but other parts of what follows are not. The level is consistent with an upper-year liberal arts course in modern physics without mathematics that is given at the University of Toronto.

Heisenberg’s Matrix Mechanics

Heisenberg’s starting point was the Bohr model of the atom. This model had been extended by Sommerfeld, and by the Summer of 1925 many physicists had learned through trial and error how to navigate through some of the morass of atomic physics. This circumstance, however, is far short from having a good theory of atomic physics.

Heisenberg attempted to build such a theory, and immediately ran into difficulties. He was attempting to make an analogy between the orbit of an electron about a nucleus and the familiar problem of a simple pendulum. However, he ended up in a “morass of complicated mathematical equations, with no way out.” (Physics and Beyond, pg. 60.) Continue reading