What we do

In 1965, Gordon Moore, one of the founders of Intel®, made an astounding observation: the capacity of computer chips – in terms of a number of transistors or computational power – doubled with each new chip generation, i.e. every 18-24 months. Mr. Moore argued that this trend, if continued, would give rise to an exponential increase in computational power with time. Today, more than 40 years after this observation, the development of computers is still obeying Moore’s law with astonishing accuracy.

Such development was possible due to continued miniaturization of the computer chip structure. For example, the Intel® Core™2 processor family is built using 45 nm technology. Industrial research and development efforts already aim at the next chip generation which will be based on light sources with a wavelength of 13 nm, which means that each elementary computational gate will consist of only a few thousands of atoms. If continued further, this trend will sooner or later reach a point where each bit of information is represented by only a few charge carriers. We shall cross a fundamental boundary where information technology can no longer rely on the laws of macroscopic world (classical physics). Microscopic, quantum mechanical phenomena will make themselves felt in technical matters.

The world according to quantum mechanics is very different from that of our everyday experience. In the classical world we do not expect wave phenomena (e.g. light waves) to behave like soccer balls nor a soccer ball to show an interference pattern when it hits the goal. Even less so do we expect the ball to traverse both goals at the same time or to change its direction in flight just because the audience is watching. But phenomena like these are common in quantum mechanics. In other words, entering the quantum domain will render most present concepts of information processing and transmission useless, replacing them with new ones. The entire field of information technology will be revolutionized in the same way discoveries of Einstein and Planck revolutionized physics some 100 years ago.

While this revolution is not due tomorrow, there is little doubt it is to happen within one or two generations. We can expect the task of aligning the theory and practice of information processing to the new requirements of the quantum age to be an enormous challenge to physicists, engineers, and computer scientists. Therefore, it is wise not to postpone this work until it becomes pressing, but begin today elaborating the new concepts, intuition, and technologies of quantum information that will replace their classical counterparts.

One may ask, if quantum technology is so much trouble, why bother with developing it instead of staying safely within the classical bounds? It turns out that the quantum revolution opens up a range of fundamentally new computational opportunities. For example, a quantum computer – a hypothetical computational device operating according to the laws of quantum mechanics – could crack the security code on our cash cards much faster than any classical computer. Another example of the astounding features of quantum mechanics is a family of communication protocols called quantum cryptography which is able to ensure the safety of data transmission on the basis of physical laws instead of numerical complexity. These protocols are already being used by banks in an attempt to improve the security of communication between branches.

There are several quantum systems that have a potential as the basis for future quantum information technology, and it is not known at present, which one is the best. Research groups all over the world are investigating advantages and disadvantages of various candidates. Our group's effort is concentrated on one such candidate – quantum light, and its fundamental particle – the photon.

Because the energy of the photon is much higher than the average temperature of the outside world, it is not likely to interact with it, thus losing the information it carries. Photons are easy to manipulate, cheap to produce, and don’t leave a mess when disposed of. Moreover, one can build an entire quantum information processor by means of single-photon sources, detectors, and simple linear optical elements such as mirrors.

The most important, unique advantage of quantum light is its ability to be an information carrier. No matter what future quantum computers will be built of, they will certainly communicate by means of photons. Even if we fail to develop quantum computers, there's still quantum cryptography - a technology which already exists today but needs improvement. Now, we can securely transmit information over 100, maybe 150 kilometers. In order to make this technology useful for everyday life, we need to enhance this range by at least an order of magnitude.

The goal of our group is to develop basic construction blocks for the future building of quantum optical technology. There are three main lines of research. In the first one we study techniques of engineering quantum light, aiming to learn how to synthesize its complex quantum states and apply them for information processing. In the second one, we construct an interface between light and atomic media to solve those quantum information tasks that cannot be solved with light alone. These are related to quantum memory, quantum repeaters, conversion of the light states between different frequency modes, and routing of quantum optical information flows. Finally, we study quantum tomography of quantum states and processes - an art of measuring quantum objects. Because quantum objects are very small, they are difficult to measure: every time we try to measure them we change them. Quantum tomography addresses this challenge by preparing multiple copies of the quantum object and performing slightly different measurements on different copies.