**Computer Scientists investigate development of Quantum Computers**

- Scientists investigate within a new research focus quantum computers and how physical procedures in nature can be calculated with help of quantum systems
- The future supercomputers could be used in fields of such as Big Data, Medicine and Data Protection
- German Research Foundation fosters the three–year project with 273.800 Euros

They could make our traditional computers look old and are supposed to solve problems which even the best supercomputers couldn’t so far: Quantum Computers. Big tec companies as Google, IBM and Microsoft currently compete about the development of the mega computer. But quantum computers are difficult to build and to programme. Jun.-Prof. Dr. Sevag Gharibian, quantum computer scientists at the University of Paderborn, wants to do his bit for a better understanding of the new supercomputers with the help of a new research project and to examine how physical procedures in nature can be calculated with help of quantum systems. His three-year project fostered by the German Research Foundation (DFG) with 273.800 Euros started in the beginning of the year.

**Research in the World of the smallest Components**

"In the Quantum Computer Science we work upon the next computer generation. Today’s computers are based on traditional mechanics and calculate with Bits. In contrast quantum computers function on the basis of quantum mechanics and calculate with quantum bits, usually called Qubits", explains Sevag Gharibian. While traditional mechanics describe mathematically how big or macroscopically objects act, quantum mechanics dedicates itself to the world of the smallest components: it examines mathematical laws which define how small or sub-atomic objects like photons, meaning tiny light particles, act.

"Thanks to the laws of quantum mechanics we know today that subatomic objects such as photons or electrons act entirely different than their counterparts in traditional mechanics. Let’s take a classical object, for instance a tennisball in movement: it can only be at one place at a time and take one state. In contrast small objects such as electrons can be at different places at the same time and exist in different states", explains Gharibian further.

For the world of computers it means: in the chip of a normal computer a bit is modelled by a processor, a traditional object. Electricity either flows or doesn’t flow through the processor. When the power is turned on the bit takes state 1, when the power is turned off it takes state 0. In quantum computers the processor is replaced by an electron, for example, a subatomic object. The bit is then modelled by the electron, part of the electron and to qubit. Same as the bit the qubit can take both state 1 and 0, but also state 1 and 0 at the same time as well as theoretically countless states in between.

**Quantum Computers can calculate way faster than previous Computers**

This ability of qubits which seems difficult to grasp at first makes quantum computers faster and more efficient than previous computers: they take significantly less time for the same amount of calculation. "In a current computer two bits can only represent one number at a time – in contrast in a quantum computer a qubit can take countless different states at the same time", describes Gharibian.

"Besides quantum computers use quantum physical phenomena of entanglement", says the computer scients. This is how qubits can be quantum interlocked, meaning being conected. If a qubit is brought into a certain state, the state of the other connected qubits is changed as well. It takes place with superluminal velocity. If several qubits are quantum entangled with each other, a quantum computer can also calculate with superluminal velocity and therefore calculate significantly faster than current computers.

**Big Data, Medicine or Data Protection: Quantum Computers are multifarious Helpers**

In the future quantum computers could be used in the area of Big Data, provide for more data protection via coding mechanisms, but also help to simulate physcial procedures which appear in nature. Gharibian: "Currently quantum computers are interesting for processing big amount of data and within the area of cryptography, the science of encryption of information – for example with the so-called shor algorithm, which uses means of quantum computer science. Besides quantum computers could help to better understand the characteristis ofthe subject matter. Therefore new medicine could be developed and new nanomaterial could be designed."

However, a lot of these plans are dreams of the future so far, since the development of quantum computers has just begun. "The research of quantum computers has intensively started in mid-nineties – with the quantum factor algorithm of Peter Shor, who revealed the flaws in the process of encrypting data. So far tec companies such as Google and special companies such as lonQ have developed first quantum computers with different technologies and performances reaching from 50 to 100 qubits", says Gharibian.

**Basic Research in "Quantum Computing Lab"**

What makes the development of quantum computers so complicated is the following: since they function according to different laws than the previous computers, it needs new programming methods. What is more: they need to be complexly cooled down extremly to low temperatures. This is when Sevag Gharibian’s research project comes into play: "In our project we want to develop algorithms and mathematical evidence for computer problems which appear in quantum systems working under very low temperatures.", explains the scientist. According to Gharibian, a central problem during the development of quantum computers is, for example, to calculate the energy of a quantum system, which has cooled down to absolute zero. Previous attempts of the so-called Theoretical Computer Science weren’t efficient enough here.

Therefore Gharibian uses different methods of Theoretical Computer Science and Mathematics in his "Quantum Computing Lab" at the University of Paderborn: "We apply techniques of algorithms and complexities theory, two branches of the Theoretical Computer Science and from Mathematics, especially algebra and algebraic geometry", explains the computer scientists. What is especially interesting for him is the so-called hamiltonian complextiy: "This special field of Theoretical Computer Science helps us to understand how quantum systems which work with very low temperatures behave."

**It is seemingly a long way to Superiority of Quantum**

In autumn 2019 Google scientists cause a sensation with an article in the journal "Nature". They claim to having shown the superiority of quantum for the first time with the help of Google’s quantum processor "Sycamore". When it comes to the superiority of quantum a quantum computer is able to solve a complex problem way faster than current super computer calculating with bits. According to Google "Sycamore" has only taken about 200 seconds for a calculation – IBM’s "Summit", which is currently the fastes super computer in the world, would have taken way longer for it. Sevag Gharibian estimates: "It isn’t clear whether Google was able to prove the superiority of quantum. IBM claimed that with a little bit of optimisation his super computer could reach almost the same results as Google’s quantum computers. So far IBM hasn’t proved it. In each case we should become aware of the following: traditional computers have been developed enormously for decades. In the foreseeable future they will probably outperform quantum computers."

Therefore quantum computers won’t replace current previous computers that fast. It isn’t decided yet when and how they will be used one day. With his research Sevag Gharibian would like to contribute to a better understanding of the super computer of the future.

More information about the research of Sevag Gharibian: https://groups.uni-paderborn.de/fg-qi