Research Highlights

In a feat of optical waveguide engineering, researchers from the Institute for Quantum Electronics at ETH Zurich have successfully observed terahertz solitons in a ring quantum cascade laser.

Traffic obstructions are not only a nuisance for our everyday mobility; they can also have negative consequences for the smallest particles such as electrons. If physicists want to study very fast dynamics in matter using soft X-rays, a clear path for electrons is required.

ETH physicists have modified one of the major schemes for quantum error correction and put it into practice, demonstrating that they can substantially prolong the lifetime of quantum states — a crucial ingredient for future large-scale quantum computers.

The demonstration of electroluminescence at terahertz frequencies from a silicon-germanium device marks a key step towards the long-sought goal of a silicon-based laser.

ETH physicists have developed the first high-repetition-rate laser source that produces coherent soft x-rays spanning the entire ‘water window’. That technological breakthrough should enable a broad range of studies in the biological, chemical and material sciences as well as in physics.

The dynamics of electrons changes ever so slightly on each interaction with a photon. The group of Prof. Ursula Keller has now measured such interplay in its arguably purest form — by recording the attosecond-scale changes associated with one-photon transitions in an unbound electron.

The creation of photoelectrons through ionisation is one of the most fundamental processes in the interaction between light and matter. Yet, deep questions remain about just how photons transfer their linear momentum to electrons. With the first sub-femtosecond study of the linear photon momentum transfer during an ionisation process, ETH physicists provide now unprecedented insight into the birth of photoelectrons.

With the demonstration of a sub-picosecond thin-disk laser oscillator delivering a record-high 350-W average output power, the group of Ursula Keller sets a new benchmark and paves the path towards even more powerful lasers.

The group of Tilman Esslinger has developed a new approach to engineer quantized gauge fields coupled to ultracold matter. The method might be the basis for a versatile platform to tackle problems ranging from condensed-matter to high-energy physics.

ETH physicists have measured how electrons in so-called transition metals get redistributed within a fraction of an optical oscillation cycle. They observed the electrons getting concentrated around the metal atoms within less than a femtosecond. This regrouping might influence important macroscopic properties of these compounds, such as electrical conductivity, magnetization or optical characteristics. The work therefore suggests a route to controlling these properties on extremely fast time scales.

In quasiparticles known as polaritons, states of light and matter are strongly coupled. The group of Prof. Ataç İmamoğlu has now developed a new approach to study nonlinear optical properties of polaritons in strongly correlated electronic states. In doing so, they opened up fresh perspectives for exploring both ingredients of the polariton: novel functionalities for photonic devices and fundamental insight into exotic states of matter.

The group of Jérôme Faist in the Institute for Quantum Electronics achieved the first demonstration of a terahertz quantum cascade laser operating without cryogenic cooling. This feat heralds the widespread use of these devices in practical applications.

The Einstein–de Haas effect, first demonstrated more than a century ago, provides an intriguing link between magnetization and rotation in ferromagnetic materials. An international team led by ETH physicist Steven Johnson now established that the effect has also a central role in ultrafast processes that happen at the sub-picosecond timescale — and thus deliver fresh insight into materials that might form the basis for novel devices.

A study exploring the coupling between heat and particle currents in a gas of strongly interacting atoms highlights the fundamental role of quantum correlations in transport phenomena, breaks the revered Wiedemann–Franz law, and should open up an experimental route to testing novel ideas for thermoelectric devices.

ETH physicists have developed an experimental platform to study the complex phases of a quantum gas characterized by two order parameters. With unprecedented control over the underlying microscopic interactions, the approach should lead to novel insight into the properties of a broad range of fundamentally and technologically important materials.

In an attosecond study of the H₂ molecule ETH physicists found that for light atomic nuclei — as contained in most organic and biological molecules — the correlation between electronic and nuclear motions cannot be ignored.

Heisenberg's uncertainty principle — the fundamental impossibility of simultaneously measuring entities such as position and momentum exactly — is at the heart of quantum theory. ETH physicists have now demonstrated an elegant way to relax this intrinsic incompatibility using a mechanical oscillator formed by a single trapped ion, opening up a route for fundamental studies and practical uses alike.

The behaviour of electrons in a material is typically difficult to predict. Novel insight comes now from experiments and simulations performed by a team led by ETH physicists who have studied electronic transport properties in a one-dimensional quantum wire containing a mesoscopic lattice.

In a semiconductor, electrons can be excited by absorbing laser light. Advances during the past decade enabled measuring this fundamental physical mechanism on timescales below a femtosecond (10^-15 s). ETH physicists now for the first time resolved the response of electrons in gallium arsenide at the attosecond (10^-18 s) timescale, and gained unexpected insights for future ultrafast opto-electronic devices with operation frequencies in the petahertz regime.

The phenomenon of metastability — when a system is in a state that is stable but not the one of least energy — is widely observed in nature and technology. Yet, many aspects underlying the mechanisms governing the behaviour and dynamics of such systems remain unexplored. ETH physicists have now demonstrated a promising platform for studying metastability on a fundamental level, using an exquisitely well controlled gas consisting of a few ten thousands of atoms.

Ultrafast lasers with multi-gigahertz pulse-repetition rates are desirable for applications requiring high sampling rates or resolvable frequency-comb lines. ETH researchers have now solved one of the long-standing problems that has hindered progress towards gigahertz diode-pumped ultrafast solid-state lasers.

Experiments based on atoms in a shaken artificial crystal made of light offer novel insight into the physics of quantum many-body systems — which might help in the development of future data-storage technologies.

Borrowing a technique developed for mapping electrical conductance in semiconductor devices, physicists at ETH imaged cold neutral atoms as they are transported through constrictions narrow enough for quantum effects to come into play. These results highlight the potential of using neutral atoms to simulate electronic transport in nanoscale devices.

Well-controlled shuttling of ions through laser beams should enable scalable quantum computing.