Researchers are on the cusp of solving some of the most difficult problems in quantum computing. A priority in this area is the current exploration of potential materials that can be used to create qubits (quantum bits) and utilized in information storage in quantum computing. Qubits are the quantum computing analogy to binary digits (bits) in classical binary computing, and they are the basis for communications, sensing and imaging. The major difference is that in binary computing the digits are either 0 or 1. In quantum computing, a qubit can be thought of as being in a state that is a combination of both 0 and 1. This is termed a superposition state, which can increase the computing power – and speed – for certain calculations by orders of magnitude.
A number of large projects across many countries are looking into suitable materials that can be used to create qubits. For example, within the EU’s Quantum Flagship initiative, the OpenSuperQ project aims to create a quantum computer consisting of up to 100 superconducting qubits, while the SQUARE and MicroQC projects use trapped ions as a basis for qubits. These projects, along with many others around the world, are focused on building a quantum computing architecture that is scalable and integrable with existing and future communication networks. Related projects in the US, for example, include work on superconducting and diamond lattice point defect qubits sponsored by the National Science Federation (NSF), and research into advanced microwave photonics at the National Institute of Science and Technology (NIST). The US Department of Energy (DOE) is also funding research into different types of qubits, such as Majorana qubits, where quantum information is encoded into the collective motions of electrons through nanowire structures.
As with quantum computing, discussion and collaboration would help guide the EU and the US to a consensus on a standard infrastructure for quantum communications.
CEOs of quantum technology start-ups interviewed for this paper confidently anticipated progress on superconducting qubit and trapped ion qubit quantum computers (examples include the Quantum Flagship’s OpenSuperQ and AQTION projects). One CEO predicted the emergence of a quantum computer with a smaller number of qubits (approximately 10–20) but with high fidelity, as well as the option of connecting to it via a cloud service, by early 2021. Several interviewees mentioned the work of Alpine Quantum Technologies (headquartered in Innsbruck, Austria), which is providing access to its trapped ion quantum computer via Cirq, an open source cloud-based quantum computing framework created by Google. Professor Dr Tommaso Calarco, coordinator of the EU’s Quantum Flagship Coordination and Support Action, anticipated the emergence of prototypes of the first integrated multiqubit superconducting chips by early 2021. These would lead to systems of around 50 superconducting qubits by September 2021, when the ramp-up phase of the EU Quantum Flagship is scheduled to end.
Predictions about the development of quantum technologies are also made in the commercial sphere. For example, a 2018 Deloitte report on quantum technology forecast that the market for quantum computers would perform comparably to other specialized computer markets (such as supercomputers) until at least the 2030s. (The report also noted the short-term value of Noisy Intermediate-Scale Quantum (NISQ) computers for a variety of sectors, such as finance and logistics.) It recommended that governments and companies take immediate action to ensure their encryption is not vulnerable to attack by quantum computers in the future as their capabilities develop.
To date, claims of ‘quantum supremacy’ have been contested and even the term is not consistently defined in the sector. A typical definition is ‘the use of a quantum computer to solve some well-defined set of problems that would take orders of magnitude longer to solve with any currently known algorithms running on existing classical computers’. The term is strongly criticized, however, by many researchers and experts, who advise that quantum computers should be judged on their ability to complete tasks that only these computers can handle – preferring instead the terms ‘quantum advantage’ or ‘quantum ascendancy’.
In 2017, Jay Gambetta of IBM Research recommended treating quantum supremacy achievements as a useful benchmark in quantum technology – in much the same way as achieving a 100-qubit quantum computer is often considered a significant step in quantum development. This approach, however, relies on using classical computing to benchmark quantum computing, which is radically different. Additionally, even after achieving such milestones, substantial research would still need to be dedicated to improving other parameters of these devices, such as maintaining high qubit fidelity to minimize errors in the results produced by such computers.
On 14 September 2019, a draft of a Google AI Quantum paper was accidentally posted to the NASA Technical Reports Server before being taken offline. The paper claimed that the Sycamore quantum computer comprised of 53 superconducting qubits sampled the output of a pseudo-random quantum circuit in 200 seconds. It was estimated that the same calculation, if performed on a number of classical computers, such as an IBM Summit supercomputer and Google Cloud servers, would take 10,000 years. As a result of this experiment, the paper claimed that Sycamore had achieved quantum supremacy.
In response, a number of IBM researchers including Gambetta wrote that a better optimized simulation of the experiment could be performed on a Summit supercomputer in a mere two and a half days. They also disputed that Google’s result demonstrated quantum supremacy, claiming that the original meaning of the term was intended to describe quantum computers performing tasks that classical computers could not.
Indeed, according to Professor Calarco:
European Quantum Communication Infrastructure
Quantum communication is a fast-growing, exciting approach to more secure communications, including quantum key distribution (QKD) and other related protocols, quantum networking, quantum internet and the use of the principle of quantum entanglement (see below for more details). In April 2019, a technical agreement was signed to foster collaboration on a European Quantum Communication Infrastructure (QCI). The agreement states the intention of preparing, between 2019 and 2020, plans for secure communication via QKD, with implementation beginning from 2021. Several EU member states have since signed up to the QCI, and an important technological step was taken in September 2019 with the launch of OPENQKD, a multidisciplinary programme for developing the first test bed for QKD.
Experts anticipate significant developments in quantum communications and networking within Europe over the next 18 months, particularly in the work of QCI, although they acknowledge that additional technological work would be needed before a quantum internet could materialize. The EU’s plans for economic recovery from the COVID-19 pandemic explicitly referenced development of quantum digital capacity and capability. The European Commission’s Directorate-General for Communications Networks, Content and Technology (DG CNECT) issued a call for tenders in September 2020 for a 15-month detailed systems study for QCI. Included within the requirements of the study are a detailed implementation roadmap, which indicates efforts towards the tangible realization of this infrastructure in the coming 10 years. Some areas of focus of the eventual QCI include quantum repeaters, amplifiers, and improved single-photon detection – all of which are required for a quantum internet.
In discussions between the EU Quantum Flagship and White House agencies there has been some buy-in predominantly on the level of basic scientific research.
Several EU Quantum Flagship projects are already investigating quantum networking devices – the QIA project seeks to connect several quantum network nodes together, as well as build improved quantum repeaters – that extend the range and reliability of quantum communication by teleportation of qubit information to intermediate stages en route, rather than sending the information in one jump and mitigating potential signal loss. The UNIQORN project is developing mass-market quantum communication devices. QMiCS (Quantitative Microwave Communication and Sensing) is developing microwave-based quantum local area networks, and QRANGE is focusing on well-established quantum random number generators (QRNGs) – truly random sources that are already being incorporated into existing devices and will be useful in both quantum simulation and for strengthening quantum key exchange.
As with quantum computing, discussion and collaboration would help guide the EU and the US to a consensus on a standard infrastructure for quantum communications. Work on common standards and common infrastructure for QKD is progressing through the International Telecommunication Union (ITU, a specialized UN agency) and the European Telecommunications Standards Institute (ETSI), which could help establish that the EU and the US could convert research into commercially competitive products in the global market – leading to faster rates of progress and increased economic efficiencies. Likewise, multi-stakeholder discussions between members of the US and EU research and industrial communities and the relevant national and supranational authorities are necessary to decide the future trajectory of encryption standards in the quantum era, given the potential impacts of quantum computing and quantum communications. A common EU–US quantum communications standard is important as the creators of such standards will gain important competitive advantages. These common standards are also a necessary condition for industrial collaboration between entities that adopt them.
Quantum sensing encompasses an increasingly well-developed set of technologies. Quantum imaging – using states of light and new detection methods that conventional imaging devices cannot achieve – is already having a significant impact in industry. Other applications for quantum sensing include medical scanners, underground mapping and new accurate timing capabilities.
On the horizon, new approaches include the experimental demonstration of quantum radar by researchers at the Institute of Science and Technology Austria. Quantum radar utilizes a split beam of entangled photons to irradiate the target, and the reflected signal is compared with the other half of the unaltered signal. This process is much more effective than classical radar at picking up low-reflective objects in noisy environments.
This demonstration has made somewhat of a splash, as it is being reported as the first experimental demonstration of a quantum radar capability – although official Chinese media claimed in 2016 that the country had already developed such systems. However, speculation in the press suggests that intentional decoherence of a quantum radar beam may be researched as a possible countermeasure.
A related technology is the development of a quantum ‘compass’ – inertial navigation sensors that use quantum states of matter to create guidance systems that retain accuracy while not relying on satellites. Previous work in this field focused on the creation of quantum magnetometers for measuring local variations in the Earth’s magnetic field (so they can be used as a navigational reference point), as well as working on a quantum gyroscope. (It must be noted, too, that more sensitive magnetometers are better at detecting submarines, which could undermine strategic military systems.)