The geometry of an electron determined for the first time



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The geometry of an electron determined for the first time

An electron is trapped in a quantum dot formed in a two-dimensional gas of a semiconductor wafer. However, the electron moves in space and, with different probabilities corresponding to a wave function, remains in some places in its confinement (red ellipses). By using the electric fields applied to the gold grids, the geometry of this wave function can be modified. (Image: University of Basel, Department of Physics)

The physicists of the University of Basel showed for the first time what an electron looks like in an artificial atom. A newly developed method allows them to show the probability that an electron is present in a space. This allows better control of the electron spins, which could be the smallest unit of information for a future quantum computer. The experiments were published in Letters of physical examination and the related theory in Physical examination B.

The spin of an electron is a promising candidate to use as the smallest unit of information (qubit) of a quantum computer. Controlling and switching this spin or pairing it with other spins is a challenge that many research groups around the world are working on. The stability of a single spin and the entanglement of different spins depend, among other things, on electron geometry, previously impossible to determine experimentally.

Only possible in artificial atoms

Scientists from the teams led by Professors Dominik Zumbühl and Daniel Loss of the Department of Physics and the Swiss Nanoscience Institute of the University of Basel have developed a method to spatially determine the electron geometry in quantum dots.

A quantum dot is a potential trap that can confine free electrons in an area about 1000 times larger than a natural atom. Since trapped electrons behave in the same way as electrons bound to an atom, quantum dots are also called "artificial atoms".

The electron is held in the quantum dot by electric fields. However, it moves in space and, with different probabilities corresponding to a wave function, remains at specific locations in its confinement.

The load distribution illuminates

Scientists use spectroscopic measurements to determine the energy levels in the quantum dot and study the behavior of these levels in magnetic fields of varying strength and orientation. On the basis of their theoretical model, it is possible to determine the probability density of the electron and thus its wave function with nanoscale accuracy.

"In simple terms, we can use this method to show what an electron looks like for the first time," says Loss.

Better understanding and optimization

The researchers, who work closely with colleagues in Japan, Slovakia and the United States, thus have a better understanding of the correlation between electron geometry and the electron spin, which should be stable on the as long as possible and quickly switchable qubit.

"We can not only map the shape and orientation of the electron, but also control the wave function according to the configuration of the applied electric fields." This gives us the opportunity to Optimizing spin control in a very targeted way, "says Zumbühl.

The spatial orientation of electrons also plays a role in the entanglement of several spins. Similar to the binding of two atoms to one molecule, the two electron wave functions must be placed on a single plane in order for the entanglement to be successful.

With the help of the developed method, many previous studies can be better understood and the performance of spin qubits can be further optimized in the future.


A trio of spin for a strong coupling


More information:
Leon C. Camenzind et al. Spectroscopy of quantum dot orbitals with magnetic fields in the plane, Letters of physical examination (2019). DOI: 10.1103 / PhysRevLett.122.207701

Peter Stano et al. Orbital effects of a strong magnetic field in the plane on a quantum dot defined by the gate, Physical examination B (2019). DOI: 10.1103 / PhysRevB.99.085308

Provided by
University of Basel


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The geometry of an electron determined for the first time (May 23, 2019)
recovered on May 23, 2019
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