A facultative course on "Quantum Computing Technology State of the Art in 2022" is offered at the ROSKA Tamás Doctoral School on Science and Technology of the Faculty of Information Technology and Bionics (ITK) of the PÁZMÁNY Péter Catholic University (PPKE). Lectures and discussions will take place on Fridays between 15.15 h and 16..45 h.

Invitation

State of the Art 2022 Case Studies of Quantum Computer Technology will be presented.

The technology of conventional digital computers between -1960 and -2010 was transistor based semi-conductor technology. For almost five decades, clas- sical computer chips and computing power have constantly improved, mainly thanks to engineers who have been able to continually shrink the components inside chips. In this process, we can fit in more components and reduce the distance electric signals travels between components, thus boosting the speed of logical operations and reducing energy consumption. This is explained by the well-known Moore;s Law, which describes how the density of industrial-produced chips has doubled every 18 months.

During the last decade, however, we have been witnessing the "end of Moore;s Law".  Scaling down the size of a transistor is limited.  All matter consists of atoms and at the atomic level, particles behave according to the laws of quantum mechanics rather than classical mechanics. Even defining 1s and 0s becomes a major problem at this level..

Quantum computing technology is far more diverse. There is a wider range of physical systems used as information carriers. In this section, we focus on technologies for realizing quantum information carriers that have received the most attention. We will begin with the most widely adopted technology thus far, namely (i) superconducting qubits. Then we turn toward quantum comput- ing systems where (ii) individual atoms (e.g. trapped ions or neutral atoms) are used as information carriers. (iii) Nuclear magnetic resonance (NMR) quantum computing will be included. Finally, we describe quantum computers based on (iv) quantum light (photons) used to store and manipulate quantum infor- mation. We are going to select Case Studies only, which have been designed, built and demonstrated. The case studies will present the competing hardware projects.

Quantum Computer Hardware State of the Art 2022

• Quantum Computers conposed of Superconducting QuBit based Quantum Circuits

Superconducting qubits are the most widely available devices from which quan- tum computing architecture of different complexity have been built. The core technology of a QuBit is the Josephson Junction consisting of two supercon- ducting metals separated by a insulator. The superconducting state requires low temperatures provided by dilution refrigerators. There are numerous ways to combine inductors, capacitors, and Josephson Junctions into varying cir- cuit designs and functionalities.  In many applications the "transmon"  design (a Josephson Junction in parallel with a capacitor) is widely used as part of different qubit architectures.

Companies advertizing their experimental superconductive Quantum Com- puters include IBM (US); D-Wave (Canada); Google Quantum AI (US); IQM Quant Comp (Finland); Alice&Bob (France); IMEC (Belgium); Microsoft Q (US); ORD Lab (India).

Thre companies (IBM, Google Quantum AI, and D-Wave already received significan commercial attention.

It is planned to select as case studies the IBM Eagle (127 QuBit), Google Sycamore (53 QuBit), and the D-Wave Quantum Annealer.

 

• Individual

  span>atoms (e.g. trapped ions or neutral atoms) used as information carriers

First, we consider ion trap quantum computing then neutral atom quantum computing. Ion trap quantum computing manipulates microscopic crystals com- posed of a handful of ionized atoms. Each ion is addressed optically to isolate and control individual qubits of quantum information. Vibrations within the micro-crystal allows for controllable interactions between the ions. Although commercially available ion trap quantum computers are smaller than super- conducting computers, the control over the quantum state is typically greater, allowing for experimental demonstration of quantum simulations and quantum error correction

. Neutral atoms are trapped and manipulated using optics. Optical tweezers use laser light to trap and arrange the atoms into a 2D array.

• Nuclear magnetic resonance (NMR) quantum comput- ing

In Nuclear Magnetic Resonance (NMR), the quantum spin of nuclei in a strong applied magnetic field is accessed and manipulated with microwave pulses. Al- though not widely pursued at the industrial level, NMR quantum computing has important conceptual significance. Many of the key quantum computing concepts were first uncovered in this context and many of the first experimental implementations were done using NMR quantum computing.

 

• In

  style="font-size:12pt;font-family:Century;"> Photonic Quantum Computers photons are used to store and manipulate quantum information

Each photon has two orthogonal directions for its polarization which can be manipulated quantum mechanically. However, the photons must be emitted in a highly correlated state before manipulation. This process of obtaining suf- ficiently correlated units of light is probabilistic, but can be heralded (i.e. a secondary flag is able to indicate a successful generation attempt). By multi- plexing entanglement generation trials,  companies such as PsiQ and Xanadu as well as national collaborations are attempting to create quantum computers with light as the primary information carrier. Photons are also called 'flying; qubits since they can be used to couple distant quantum devices for computa- tional or cryptographic purposes. .

It is planned to select as case study Xanadu;s photonic quantum computer.

Future of Quantum Computing: News-full or Use- full?

The promise of quantum computing is that it will help us tackle certain types of problems that today;s classical computers cannot solve in a reasonable amount of time. It is important to note that quantum computing does not provide a universal solution for al

l computing problems, but it offers solution for most "needle in a haystack" types of search and optimization problems.

Many large computer companies are investing billions of dollars into building quantum computers. Similarly, many academic institutions are also investing a lot of brainpower into this area. The current generation of quantum computers need to be managed by expert staff due to their specialized hardware and cooling requirements. As a result, in the near future, quantum computing functionality are and will be mostly offered as a cloud service.

In 2019, IBM and Google demonstrated that quantum computing is a prac- tical reality, instead of a theoretical possibility. We still hadn;t built physical qubits that could last as long as we wanted, but we built them to last long enough to do some specific calculations faster than the world;s most powerful supercomputer. At this point, the border has been crossed from pure classical computing into a Noisy, Intermediate Scale Quantum (NISQ) computing era.

NISQ computers can perform tasks with imperfect reliability, but beyond the capability of classical computers. Even with imperfect reliability, we can ad- vance our knowledge of science in the NISQ era. However, having access to the hardware of NISQ type quantum computers, to exploiut their potential a lot of software research and development needs to be done. In March 2022 Wikipedia listed 92 companies majoring in quantum computing.  The majority of them are focusing on software development. A case study of Google Quantum Arti- ficial Intelligens demonstrates the road from NISC hardware to breakthroughs in simulations in chemistry, material science and machine learning.