Researchers succeed in imaging quantum events

Quantum technology is a growing field of physics and engineering which utilizes properties of quantum mechanics as a basis for advanced practical applications such as quantum computing, sensors, information, communication and medicine. This promises to lead to a new era of technology unlike anything we've known. Computers will be much more powerful, medical treatment will be non-invasive and far safer than today, and even teleportation can be envisioned. A phenomenon that stands at the core of this development is the Quantum phase transition.

Phase transitions are present in our day-to-day life, starting from the water boiling for our morning coffee to the melting of an ice cube in our drink. In these phase transitions between solid, liquid, and gas phases, we can directly visualize certain aspects of the transition. We see bubbles of one phase in the other—forexample bubbles of air in boiling water, or droplets of water in ice slush. In order to see these phase transitions, we need nothing but our eyes. These "classic" phase transitions, with which we are all familiar, have a common characteristic which is that their driving force is temperature. Ice melts at zero degrees Celsius and evaporates at a hundred degrees. How cool would it be if instead of heating water in a kettle for a cup of tea we could take a glass of cold water and boil it by bringing it close to a magnet! In our world this is impossible but in the quantum world it works.

The scientific community has recently gained increasing interest in a different type of phase transitions—"quantum phase transitions"—which occur at the absolute zero temperature (minus two hundred andseventy three degrees). These transitions are not driven by the temperature, but by changing a different physical property such as mechanical pressure or magnetic field. Similar to classical phase transitions, quantum phase transitions are also accompanied by the presence of "bubbles" of one phase in the other. The scientific term for these bubbles is Quantum fluctuations. Unlike the classic case, where a change in the temperature is responsible for the bubbles, in the quantum case the bubbles arise due to the uncertainty principle which is one of the basic rules in quantum physics. This principle, developed by German physicist Werner Heisenberg, states that contrary to our intuition, vacuum is not empty but contains temporary changes in the amount of energy in a point in space. These changes lead to quantum bubbles of one phase into a second phase even at the absolute zero temperature.

Until now it has been impossible to take pictures of these quantum fluctuations. They occur at very low temperatures, and many times involve physical phases which cannot be seen by a regular microscope. Though indirect evidence for their presence appears in many measurements, no one has actually seen them. But an international group led by Prof. Beena Kalisky and Prof. Aviad Frydman, from the Department of Physics and the Institute for Nanotechnology at Bar-Ilan University in Israel, has succeeded in imaging quantum fluctuations for the first time. In their experiment, published today in Nature Physics, not only were quantum fluctuations visualized, but new information about the sizes, times and distributions of quantum events was extracted.