#### Uncategorized

# Quantum Transport Goes Ballistic

March 27, 2017 | Written by: IBM Research Editorial Staff

Categorized: IBM Research-Zurich | Nanotechnology | Quantum Computing

Share this post:

Published today in the peer-reviewed journal Nano Letters, IBM scientists have shot an electron through an III-V semiconductor nanowire integrated on silicon for the first time. This achievement will form the basis for sophisticated quantum wire devices for future integrated circuits used in advanced powerful computational systems.

IBM scientist and lead author on the paper Dr. Johannes Gooth explains the paper in this Q&A.

**The title of your paper is Ballistic one-dimensional InAs nanowire cross-junction interconnects. When I read “ballistic” rather large missiles come to mind, but here you are doing this at the nanoscale. Can you talk about the challenges this presents?**

**Johannes Gooth (JG):** Yes, this is very similar, but of course at a much different scale. Electrons are fired from one contact electrode and fly through the nanowire without being scattered until they hit the opposed electrode. The nanowire acts as a perfect guide for electrons, such that the full quantum information of this electron (energy, momentum, spin) can be transferred without losses.

We can now do this in cross-junctions, which allows us to build up electron pipe networks, where quantum information can perfectly be transmitted. The challenge is to fabricate a geometrically very well defined material with no scatterers inside on the nano scale. The template-assisted selective epitaxy or TASE process, which was developed here at the IBM Zurich Lab by my colleagues, makes this possible for the first time.

**How does this research compare to other activities underway elsewhere?**

**JG:** Most importantly, compared to optical and superconducting quantum applications the technique is scalable and compatible with standard electronics and CMOS processes.

**What role do you see for quantum transport as we look to build a universal quantum computer?**

**JG:** I see quantum transport as an essential piece. If you want to exercise the full power of quantum information technology, you need to connect everything ballistic: a quantum system that is fully ballistically (quantum) connected has an exponentially larger computational state space compared to classically connected systems.

Also, as stated above, the electronics are scalable. Moreover, combining our nanowire structures with superconductors allows for topological protected quantum computing, which enables fault tolerant computation. These are major advantages compared to other techniques.

**How easily can this be manufactured using existing processes and what’s the next step?**

**JG:** This is a major advantage of our technique because our devices are fully integrated into existing CMOS processes and technology.

**What’s next for your research?**

**JG:** The next steps will be the functionalization of the crosses, by means of attaching electronic quantum computational parts. We will start to build superconducting/nanowire hybrid devices for Majorana braiding, and attach quantum dots.

Universal quantum computer here we come.

**Ballistic one-dimensional InAs nanowire cross-junction interconnects,** Johannes Gooth, Mattias Borg, Heinz Schmid, Vanessa Schaller, Stephan Wirths, Kirsten E Moselund, Mathieu Luisier, Siegfried Karg, and Heike Riel, Nano Letters, **DOI:**10.1021/acs.nanolett.7b00400, Publication Date (Web): March 23, 2017

### IBM Supports Q2Work Education Initiative

The need for a future workforce with a robust set of quantum computing skills drives our support for Q2Work, the National Science Foundation-funded initiative led by the University of Illinois and the University of Chicago to provide quantum education, programs, tools, and curricula to K-12 students.

### Quantum Conundrum: Clifford Group Investigation Unexpectedly Reveals New Quantum Advantage Proof

When we began our current line of investigation, the goal was to study the structural property of the Clifford group, describing a set of transformations that generate entanglement, play an important role in quantum computing error correction, and are used in (randomized) benchmarking. In a series of one-thing-leads-to-another findings, however, we ended up discovering a new mathematical proof of quantum advantage – the elusive threshold at which quantum computers outperform classical machines in certain use cases.

### IBM Roundtable: Building a Quantum Workforce Requires Interdisciplinary Education and the Promise of Real Jobs

The ability to harness quantum-mechanical phenomena such as superposition and entanglement to perform computation obviously poses a number of difficulties. Add in the need to make these systems perform meaningful work, and you’ve raised the stakes considerably. Creating a pipeline of talented, well-trained academics and professionals who can meet those challenges was the subject of IBM’s July 28 virtual roundtable, “How to Build a Quantum Workforce.” Watch the replay, here.