Department of Applied Physics

QCD Media

QCD research in the media
An artistic illustration shows how microscopic bolometers (depicted on the right) can be used to sense very weak radiation emitt
An artistic illustration shows how microscopic bolometers (depicted on the right) can be used to sense very weak radiation emitted from qubits (depicted on the left). Photo: Aleksandr Käkinen/Aalto University

New method of measuring qubits promises ease of scalability in a microscopic package

Aalto University researchers are the first in the world to measure qubits with ultrasensitive thermal detectors—thus evading the Heisenberg uncertainty principle

Chasing ever-higher qubit counts in near-term quantum computers constantly demands new feats of engineering.

Among the troublesome hurdles of this scaling-up race is refining how qubits are measured. Devices called parametric amplifiers are traditionally used to do these measurements. But as the name suggests, the device amplifies weak signals picked up from the qubits to conduct the readout, which causes unwanted noise and can lead to decoherence of the qubits if not protected by additional large components. More importantly, the bulky size of the amplification chain becomes technically challenging to work around as qubit counts increase in size-limited refrigerators.

Cue the Aalto University research group Quantum Computing and Devices (QCD). They have a hefty track record of showing how thermal bolometers can be used as ultrasensitive detectors, and they just demonstrated in an April 10 Nature Electronics paper that bolometer measurements can be accurate enough for single-shot qubit readout.

Nature Electronics (2024)

Media coverage in English:  Aalto University 

Media coverage in Finnish: Aalto Yliopisto

Artistic illustration of an Alice ring, which researchers have just observed for the first time in nature. Credit: Heikka Valja/Aalto University.
Artistic illustration of an Alice ring, which researchers have just observed for the first time in nature. Credit: Heikka Valja/Aalto University.

Quantum discovery offers glimpse into other-worldly realm

Experiments promote a curious flipside of decaying monopoles: a reality where particle physics is quite literally turned on its head

Dubbed the ‘Alice ring’ after Lewis Carroll’s world-renowned stories on Alice’s Adventures in Wonderland, the appearance of this object verifies a decades-old theory on how monopoles decay. Specifically, that they decay into a ring-like vortex, where any other monopoles passing through its centre are flipped into their opposite magnetic charges.

Nature Communications 14, 5100 (2023)

Media coverage in English:  Aalto University, PhysicsWorld, NewScientist, ScienceAlert, PopularMechanics, DayFR Euro, Nanowerk, Knews.media, Extension13, UnfoldingMatrix, DevHardware, NewsOasis, TheSun  

Media coverage in Finnish: Aalto Yliopisto, Sttinfo.fi, Tekniikka&Talous, Iltalehti

Other: Dasschoenespiel (DE), Prematch.com (AR), SoestNu (NL), PRKernel (BG), Magyar24 (PL), Yplay (CZ)

Image of the power sensor on a silicon chip. Credit: Jean-Philippe Girard/Aalto University
Image of the power sensor on a silicon chip. Credit: Jean-Philippe Girard/Aalto University

QCD's new paper as a result from an amazing collaboration with Bluefors!

Cryogenic sensor enabling broad-band and traceable power measurements | Review of Scientific Instruments | AIP Publishing

Media coverage in Finnish: Aalto yliopisto, Aamuset, STT info, Uusi Teknologia, Tekniikka & Talous

Media coverage in English: Bluefors, ScienceDaily, Aalto University, SwiftTelecast, VerveTimes, Crumpe, EurekAlert!, nanoverk, physorg, scienmag, Bioengineer, AZO Quantum, Photonicsonline, Statnano, india Educationdiary.com, GEOMORES

Artistic impression of a unimon qubit in a quantum processor. Credits: Aleksandr Kakinen.
Artistic impression of a unimon qubit in a quantum processor. Credits: Aleksandr Kakinen.

Unimon - A new qubit to boost quantum computers for useful applications

A group of scientists from Aalto University, IQM Quantum Computers, and VTT Technical Research Centre of Finland have discovered a new superconducting qubit, the unimon, to increase the accuracy of quantum computations

Nature communications 13, Article number: 6895 (2022)

Media coverage in Finnish: Tekniikan Maailma, STT, Tekniikka&Talous, Aalto

Media coverage in English:

Businesswire, Phys.org, Tech Explorist, yahoo!Finance, 01net., New electronics, Morocco Detail Zero, MENAFN, NewsWire, BusyContinent

Media coverage in French: IT epresso

Media coverage in German: Boerst.de

In Borromean rings, each circle holds the pattern together by passing through the other two circles. Image: Alexandr Kakinen
Artistic impression of a unimon qubit in a quantum processor. Credits: Aleksandr Kakinen.

A peculiar protected structure links Viking knots with quantum vortices

Mathematical analysis identifies a vortex structure that is impervious to decay

Scientists have shown how three vortices can be linked in a way that prevents them from being dismantled. The structure of the links resembles a pattern used by Vikings and other ancient cultures, although this study focused on vortices in a special form of matter known as a Bose-Einstein condensate. The findings have implications for quantum computing, particle physics and other fields.

Communication physics, 5, 2022

Media coverage in Finnish: Aalto Yliopisto

Media coverage in English:  Aalto University, REVYUH, MIRAGE, SCIENMAG, SciTechDaily, PHYSORG, 

Media coverage in Italian: Meteoweb

Media coverage in Spanish: ABC de Sevilla Ciencia

From left: Mikko Möttönen, doctoral student Arto Viitanen, and Valtteri Lahtinen, who recently launched the Quanscient startup. Photo: Mikko Raskinen.
From left: Mikko Möttönen, doctoral student Arto Viitanen, and Valtteri Lahtinen, who recently launched the Quanscient startup. Photo: Mikko Raskinen.

Mikko Möttönen and his team aim to rein in qubit errors. The research project recently received €2.5 million from the EU to develop a more accurate type of a qubit.

Artistic impression of an on-chip microwave source controlling qubits. Credit: Aleksandr Kakinen
Artistic impression of an on-chip microwave source controlling qubits. Credit: Aleksandr Kakinen

A new super-cooled microwave source boosts the scale-up of quantum computers

Nature Electronics, DOI, (2021)

Graphene bolometer artistic image
Artistic image of a graphene based bolometer.

Bolometer operating at the threshold for circuit quantum electrodynamics

Nature, 586, 47–51(2020)

Microscop image of the nanobolometer
Colored electron microscop image of the nanobolometer. The dark oval at the bottom left represents a 1.3-micrometer-long Ralstonia mannitolilytica bacterium. Credit: Roope Kokkoniemi/Aalto University.

Nanobolometer with ultralow noise equivalent power

Communications physics, 2, 124 (2019)

Superconductor-insulator-normal metal tunnel junction
False-colour scanning electron micrograph of the two superconductor–insulator–normal-metal (SIN) tunnel junction. Scale bar, 5 μm.

Broadband Lamb shift in an engineered quantum system

Nature Physics,15, 533–537 (2019)

Particle densities related to the decay of the quantum knot
Particle densities related to the decay of the quantum knot (left), which surprised researchers by untying itself after a few microseconds and eventually turning into the spin vortex [Image credit: Tuomas Ollikainen/Aalto University]

Decay of a Quantum Knot

Physical Review Letters 123, 163003 (2019).

Artistic impression of qubit readout using the quantum states of a resonator
Artistic impression of qubit (blue chip) readout using the quantum states of a resonator (blue and red jets). Figure credit: Heikka Valja.

Qubit Measurement by Multichannel Driving

Physical Review Letters 122, 080503 (2019)

Photo of a quantum circuit
Photo of a quantum circuit on a sample holder

Construction of a quantum computer

artistic image of an Dirac monopole
Artistic impression of a Dirac monopole

Experimental Realization of a Dirac Monopole through the Decay of an Isolated Monopole

Physical Review X 7, 021023 (2017).

Refrigerator for quantum computers

Quantum-circuit refrigerator

Nature Communications 8, 15189 (2017).

Artist image of an superconducting microwave detector
Artist image of a superconducting microwave detector

Detection of zeptojoule microwave pulses using electrothermal feedback in proximity-induced Josephson junctions

Physical Review Letters 117, 030802 (2016).

Quantum-limited heat conduction over macroscopic distances

Nature Physics 12, 460–464 (2016).

Experiemental setup used to watch quantum knots untie
The experimental set-up at Amherst College where quantum gasses are made [David Hall/Amherst College]

Tying Quantum Knots

Nature Physics 12, 478–483 (2016). 

Observation of isolated monopoles in a quantum field

Science 348, 544 (2015). 

 Click here to access the paper for free!

An Accurate Single-Electron Pump Based on a Highly Tunable Silicon Quantum Dot

Nano Letters 14, 3405–3411 (2014).

Quantum-mechanical monopoles
Images of the condensate showing the integrated particle densities

Observation of Dirac Monopoles in a Synthetic Magnetic Field

Nature (London) 505, 657-660 (2014).

*DISCLAIMER: Some of the linked articles use the term ‘magnetic monopole’ rather freely and hence may give the wrong impression that we have observed the magnetic monopole as an elementary particle. What we have actually observed is an analogous object in a Bose-Einstein condensate, a situation which closely realizes the theory in Dirac’s 1931 paper but does not realize the exact physical scenario of a monopole in the physical magnetic field. This is why we refer to our finding as a synthetic magnetic monopole or a Dirac monopole, where the latter term refers to the theoretical description that Dirac found, not the physical set-up that has not been realized thus far.

Single-shot Readout of an Electron Spin in Silicon

Nature (London) 467, 687-691 (2010).

Transport Spectroscopy of Single Phosphorus Donors in a Silicon Nanoscale Transistor

Nano Letters 10, 11-15 (2010).

Creation of Dirac Monopoles in Spinor Bose-Einstein Condensates

Physical Review Letters 103, 030401 (2009).

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