Combining low temperatures and high frequency signals is becoming ever more important in the development of quantum technologies. In QuTech for example transmon based devices use some signals in the 2-10 GHz range and spin qubits use even higher frequencies; over 20 GHz. It is desired that the noise in the working bandwidth should be as low, and as cold, as possible, but these devices can be also quite susceptible to unwanted photons at much higher frequencies, 50-100 GHz, leading to extra quasiparticle generation or photon assisted tunneling that can destroy the fragile quantum states. This post aims to be an easy to read tutorial and guide as we look at a model to reduce the distribution of thermal photons from a high temperature to a low one. In the particular case of a 1-dimensional coaxial cable carrying photons from room temperature towards a cold sample mounted in a dilution refrigerator. I’ll try to convey some intuition how this model behaves and what this means for cryogenic design.
by Sara Marzban
In this post I’m going to briefly describe the solid state system, namely rare-earth crystalline material, that the Tittel lab at Qutech is using to do all sorts of cool quantum communication experiments, including building the hardware required for an elementary link of a quantum repeater.
In this era of online communications, the security of transmitted and received information is extremely important. Quantum communication is an absolutely secure method of communication between points A and B. However, building these secure quantum communication networks has proven to be difficult. In a quantum communication network, fragile quantum states are transmitted between a transmitter (point A) and a receiver (point B). During transmission, decoherence can be introduced into the system, either from losses in the transmission line, absorption in the system or from environmental contamination. Some of the losses occurring over the full length of the transmission line scale exponentially with distance and as a consequence, quantum communication is restricted to a range of about 200 km, beyond which quantum states can no longer be reliably measured [1, 2, 3].
Continue reading Have you ever been to Ytterby?
With QuTech expanding from a quantum transport research group to a large institute focusing on quantum computers, the number of people walking around in the hallways expands. It makes you almost forget that there are also people leaving. But as the seasons go by, PhD students at QuTech come and go. It gives QuTech its characteristic dynamic character. But it also brings sadness every time we have to wave someone goodbye. And this is exactly what this blogpost is about. Since editorial duties for this blog are performed on a volunteer basis by PhD students (in what little remains of their free time), this means that any editor’s tenure is inherently limited by his or her PhD track. Therefore, with some sadness, we have to say goodbye to Jonas, the founding father of the QuTech blog and involved from the very start. He finished his PhD and moved to Amsterdam. He was an amazing and creative member of the team and we would like to thank him for the time he has spent making this blog an inspirational place for quantum computing.
But of course he wouldn’t leave without equally capable replacement. And, since QuTech is growing, we also extended the editorial team. That is why we proudly announce the two newest team members, Tim and Matteo. Actually Tim and Matteo have been active on the blog for a while. So the time is definitely there for a more official introduction. Continue reading A word from an editor emeritus and new blog team members!
by Adriaan Rol
Last week Google and collaborators published a paper in which they claim to have achieved Quantum Supremacy, one of the major milestones in quantum computing. The idea of quantum supremacy is to use a programmable quantum device to perform a task that is out-of-reach for any classical computer. Google claims to have solved a problem in seconds that would take tens of thousands of years on a state of the art supercomputer. The quantum supremacy experiment has been a long-standing milestone in the field of quantum computation, and as such, skepticism has arised; soon after publication of the article a group in IBM research has challenged the results .
Rather than joining in on the controversy of whether or not Google has really achieved quantum supremacy , I want to focus on some more basic questions: what is quantum supremacy, how does one demonstrate quantum supremacy and why is this such an important milestone?
Continue reading Quantum Computational Supremacy
by Bas Dirkse
The internet as we know it today has become an integral part of our lives. We use this piece of technology on a daily, hourly, almost continuous basis. We use it at work, to relax, to socialize, to fact check our friends during an argument and even to control the thermostat at our homes. We can definitely claim that, despite the internet bubble in the 90’s, the technology has far outperformed its expectations of the early 60’s and 70’s in the societal and financial benefits it provided. Will the same bright future be reserved for the quantum internet? Will it deliver the same amount of societal and financial benefits to the world as its classical sibling has done? Continue reading Quantum internet: at the verge of an emerging technology
by Floor van Riggelen
Take a close look at this famous picture. These are the people who attended the fifth Solvay International Conference (1927), where the leading physicists of that time discuss the newly formulated quantum theory. What stands out to me is that this is quite a homogeneous group: 28 white (including Jewish), middle aged guys, plus Marie Curie. Of course, these were different times. Comparing this to QuTech in Delft, the place where I work, (an example of a physics research environment in general) there are some improvements when it comes to diversity. Currently 23% of the QuTech employees are non-European and 17% percent are female, according to a recent official review . However, a quick count on the QuTech webpage will tell you that if you only look at scientists and technical staff , this percentage drops to about 10%. At QuTech there are still several scientists who are the only woman in their research group. Looking at it in this way, it seems that not much has changed in almost 100 years of quantum physics. Continue reading Counting women in physics
by David Maier
QuTech not only offers a wide range of interesting research, but also a diverse group of employees from numerous countries around the world. As a student from the far away country of Germany I was very curious if I would be able to fit in and overcome the cultural differences. Four months ago I came to Delft for my master’s project. In this little piece I would like to tell you from a humorous perspective about some of the challenges I faced as an international student coming to Delft and how you can overcome them too.
Disclaimer: this text contains irony.
Continue reading Diary of an international student at QuTech
by Christophe Vuillot
Quantum physics is the strange and counterintuitive theory of physics governing the tiny world of atoms, electrons and photons. To access such small and ephemeral phenomena, scientists deploy advanced techniques to isolate and manipulate what can be destroyed by the tiniest breeze. Can they further protect these phenomena and make them survive to reach the scale of our life? This will be required to build a functional quantum computer. Continue reading Quantum Information Needs Protecting, and Here’s How to Do It
by Axel Dahlberg
Summer is approaching fast! The days until vacation are getting fewer and fewer. But before you can relax at a beach with a cold drink you need to send a bunch of emails. However for some reason the software allowing your computer to connect to the Internet has suddenly vanished. What can you do? Well, maybe you can just manually do whatever this software does. It can’t be too hard right? Or can it…?
The network stack, a collection of of software used by computers to connect to each other and run applications over a network, such as e-mail, social media, file sharing, video streaming etc., used by today’s Internet is crucial to its operation. You use it everyday, but do you know what it actually does? When you send an email to your colleague, how is your email actually transmitted across to a different computer?
by Barbara Terhal
Recently I had to deal with some bureaucratic business involving a European grant. It concerned the transfer of this grant from one academic institution to another in the form of an amendment.
The transfer had to take place through the interaction of a variety of people, project managers, scientists, upper- and lower-level secretaries, in a EU web portal.
The portal is somewhat like a virtual castle in which one occasionally discovers a door to a hidden room. Once open, the hidden room turns out to give access to new functions and role play, inviting to dress-up and bal masqué, going far beyond the promise of the