A Quantum Carol

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by Helsen, Kroll, Rol and van Dam

The phone was ringing in the lab, Sophie let it ring a few times before looking up from her experiment. She was a bit annoyed until she realized what time it was, almost midnight and she had only just got the experiment running. She picked up the phone, half expecting to hear her advisor when she heard her mother’s voice:

“Sophie, we were worried about you, you didn’t pick up your phone and it has been almost four hours!”.

“Don’t worry Mom, I’ll be right there, I just have to set up a measurement run overnight, otherwise the experiment will be doing nothing over Christmas!”

“But dear, like you said, it’s Christmas, you promised you’d be here! You know how Granny has been looking forward to seeing you.”

“OK, OK I’ll just start what I have now, but I still have to refill the traps. I’ll be there in 10 minutes”, she said as she hung up the phone.

As the nitrogen traps overflowed, a haze covered the floor and she started to feel a bit dizzy…

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Towards paving the way for signatures of quantum physics

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by Michiel de Moor

Even if you’re in a niche research field, it seems almost impossible to keep up with all the scientific literature that has been coming out in the past couple of years. There are estimations that the global scientific output doubles every 9 years, so it’s not going to get any easier. If you want people to read about your results, you’ll have to stand out. An important part of standing out is having a good abstract.

The abstract contains the essence of the story, and summarizes the most important results. Skimming over the abstract is usually the first filter people apply to figure out whether or not a paper is worth reading in detail. In this sense, the abstract is like the window display of a department store, designed to lure people inside.

Designing a window display is big business, and over the years many courses have popped up that teach aspiring researchers how to write better papers and capture their intended audience. Archetypical phrases can help to quickly communicate meaning: because people are familiar with the phrase, it takes them less effort to get the information contained in it. However, as with most things that get overused, the meaning of these phrases can be lost or transformed over time.

Below are a few phrases that I’ve encountered regularly in physics papers, what signals they send, and what to look out for when using/reading them.

1. <Research field X> has received a lot of attention recently.

By signalling which research field you think your research belongs to, you show people who belong to the same “tribe” that this paper should be of interest to them. It also allows you to place your contribution in a broader context. The proliferation of increasingly specialized journals is a double-edged blade in this case: it facilitates publishing about tiny details of a larger issue, but it also makes it more difficult to connect to researchers outside your tribe. Additionally, it can create an echo chamber, where the same reasons for the field’s existence keep being repeated until they become dogma. Be aware of your intended audience, especially if you’re trying to step across tribal lines and connect with a more general subset of physicists.

2. We find clear signatures of <X>

Sometimes, experimental results can be very clearly explained by an elegant physical model, both qualitatively and quantitatively. Sometimes, while the model doesn’t exactly line up with the experimental results, it paints the same broad-strokes picture while making minimal assumptions. And sometimes, the signal you measure ventures into “Jesus shaped potato chip” territory. Calling your results “signatures” gives the clear signal that a) there’s definitely something here and b) it’s not clear what that something is. And this is okay! Just because you don’t know what’s happening doesn’t mean the observation has no value to others. It is important not to speculate too wildly though: extraordinary claims still require extraordinary evidence.

3. These results pave the way for <X>

This signal tells your audience that not only is this result intrinsically valuable, it also serves as an enabling technology for other things they might find interesting. By “paving the road”, you suggest that all obstacles to further progress have been eliminated. However, it’s important to recognize that not all roads are created equal. For example, even if you manage to go down a steep, winding mountain road on a unicycle, there’s no guarantee you’ll be able to do it again. Also, remember that a piece of road is generally not considered useful if it doesn’t connect to a larger network. Because of this, it can be tempting to try to connect a slightly dull result to a more exciting bigger goal in an attempt to get people to pay attention to your paper. If you can justify this, for example because your results might be relevant for a certain community in a way that is not obvious (see point 1), then go for it. Keep in mind, though, that a lot of people also use this tactic as a form of scientific clickbait.

Conveying the results of months (or even years) of hard work in a clear, concise manner is one of the most difficult parts of science (at least, for me it is!). The kinds of phrases I described here can serve as crutches to help you get started on the difficult path towards writing better papers. But just like real crutches, at some point you’re better off casting them aside and learning to walk by yourself.

 


michielMichiel de Moor is an experimental physicist working on topological quantum computer. He spends most of time in a loop of fabricating quantum devices and measuring quantum devices. When he’s not working in the cleanroom, he enjoys seemingly pointless discussions and taking part in pub quizzes. Groundhog Day is one of his favorite movies.

 

The first Delft qubit

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By Hans Mooij

Introduction

When did we have our first quantum bit? To answer, one needs to agree on the definition. When does a two-level system become a qubit? In my view, only when coherent quantum dynamics is demonstrated. In the summer of 2002, Rabi oscillations of a superconducting flux qubit were observed in our laboratory. They were published in Science [1]; the primary authors were Irinel Chiorescu (postdoc, now professor at Florida State University) and Yasunobu Nakamura (on sabbatical from NEC Japan, now professor at University of Tokyo). As we all know, much has happened in the years after. Here I want to describe what happened before. How did we come to this point? I concentrate on my personal story and on superconducting circuits. In our Quantum Transport group we had the parallel research line on semiconductor quantum dots by Leo Kouwenhoven and his people that led to our first spin qubit in 2006.

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Inside Intel

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By Jelmer Boter

In the fall of 2015 QuTech and Intel Corporation joined forces in an active collaboration working on the realisation of a quantum computer. The collaboration comprises comprises Edoardo Charbon’s control electronics, Koen Bertels’ architecture work, Leo DiCarlo’s superconducting qubits and Lieven Vandersypen’s silicon spin qubits. After having worked on the Delft side of the spin qubit part of that collaboration for almost two years, I spent three months this summer in Hillsboro, Oregon to be on the other side of the phone in our weekly Skype meetings. In this blogpost, I will share some of my experiences with you.

The writer at the entrance of an Intel building

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Bob, say something if you quant hear me!

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Perhaps you have become convinced that sharing quantum entanglement with a distant party is a useful resource. By itself, it might not allow you to communicate the weather to your grandmother, but, if pure enough, and assisted by some classical communications, it does allow you to win funny card games or, (perhaps) more importantly, to transmit quantum information via teleportation. The question is, how do we manage to share quantum entanglement with a distant party in the first place? Here, I want to discuss what are some of the challenges for establishing long-distance entanglement and a very idealized solution.

Let us consider that two distant parties, that we call (surprise) Alice and Bob, are connected via a quantum channel. A quantum channel is just a channel that allows us to transmit quantum information. The typical example of a quantum channel for connecting distant parties is a cable of optical fibre. Hence, let us assume that Alice and Bob are connected via some long optical fibre cable. Since I am a theorist, we also imagine that Alice and Bob have noise-free quantum memories available to them and, even more, they can transfer qubits from their memories to the input of the channel and store incoming qubits into the memory without any error or decoherence.

Alice prepares an entangled state locally between two qubits in her memory.

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Hiding Schrodingers cat: a qubit of quantum error correction

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by Tom O’Brien

If you’re reading a blog named ‘bits of quantum’, I guess I can assume you know a little bit about quantum computing and have a rough idea of what a qubit is. And, if you’ve read some of the previous articles on this blog, you may have gotten some idea of how difficult it is to make one. Being a quantum mechanic is real tough work, man!

Probably the largest challenge in quantum computing right now is minimizing the rate at which errors accumulate as you perform a computation on your quantum chip. In classical computers (your PC, or mobile phone), this is pretty much a solved problem. The probability of an error in any given operation is usually less than 1 in 1,000,000,000,000,000. This means in the process of me writing this blog post and it popping up on your screen probably less than one error has occurred. They’re not perfect, but after 50+ years of research and refinement, computers are pretty damn good these days.

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How to make artificial atoms out of electrical circuits – Part II: Circuit quantum electrodynamics and the transmon

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by Christian Dickel

There are different kinds of scientific papers. Some are like James Joyce’s Ulysses – you really want to read them but you have never made it through. There are the English classics – they are timeless and awe-inspiring. Like Shakespeare, some papers have changed the english language and, for example, teleported the wrong ideas into the heads of numerous journalists. In my group, we have a Harry Potter paper that we read again and again and keep discovering new insights. This is Jens Koch et al.’s 2007 classic “Charge insensitive qubit design derived from the Cooper pair box”, which introduced the transmon qubit.

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Around the World in 40 Days (Part One)

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By James Kroll

Research in academic is a tough, gruelling but ultimately rewarding job (otherwise we wouldn’t work so hard at it!). Usually if you ask a scientist about what it is like to work in research, you will be subjected to a coffee fuelled rant about tiresome data analysis, demanding students and endless paper preparation. Unless you catch us in an unusually good mood we won’t take the time to talk about the many things about our job that we genuinely enjoy.

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Research mentality at the Applied Physics sports day

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by Suzanne van Dam

Last Thursday was the yearly Applied Physics sports day. As is tradition, QuTech participated in big numbers. We competed with three teams, and it was clear already from the start that the goal of the day was not just to participate, it was also to win!

The QuTech team.
Figure 1: The QuTech team.

The winners mentality of the QuTech teams made me wonder: why were we more competitive than the average student team? Is there an analogy between sports and research that underpins this?

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The remarkable effectiveness of math

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by Jonas Helsen

So this post will be a bit more, let’s say, philosophical. I’d like to share some of my thoughts on a particular subject which has always struck me when I was studying physics and also now while I’m doing it in what might be called a professional fashion. That subject is mathematics. More precisely it is mathematics as applied to physics. Now I won’t pretend to be anything close to a real mathematician, but when you need a math-person and there are no mathematicians around you can probably do worse than a theoretical physicist. In physics, and also in computer science, we use math; a lot of it. In fact I would say that, and I think most physicists would agree with me, that mathematics is the language the universe is written in. Or at least the only language capable of describing it in an efficient manner. People often marvel at the ability of mathematics to capture physical phenomena in an extremely accurate and efficient manner, often waxing philosophically about the inherent simplicity of the universe. Here I’d like to give some of my, fragmented and incomplete, thoughts on the matter. While I certainly think that the fact that nature is describable at all is a fact worth pondering over long and hard I think the prevalence of math in physics and its remarkable effectiveness is at least partly due to decidedly more down to earth cultural forces present throughout the history of mathematics.

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