Quantum technology

When we think of quantum technology, many of us immediately envision the quantum computer. However, quantum sensors and quantum communication hold just as much potential, and the entire development within quantum technology could radically change our world.

Postdoc Santiago Tarrago Velez is setting up an experiment in the cryostat, that cools down to near absolute zero, in order to study coupling between light and mechanical oscillations at the quantum physical level. Foto: Bax Lindhardt

The applications of quantum technology are still so new that scientists cannot predict precisely which areas will be most impactful. However, here are three possibilities that many researchers believe in:

  • Quantum computers could make a significant difference in solving computation problems within logistics, finance, and medicine, for example.
  •  The ultra-sensitive properties of quantum sensors could be in high demand, especially for medical purposes and in the military.
  • Quantum communication and encryption offer promising data security solutions relevant to all aspects of society.

Although we have known about quantum mechanics since Niels Bohr and other scientists made their groundbreaking discoveries in the 1920s, it is only in recent decades that development has accelerated. We have now come to a point where we can control and manipulate certain quantum physical properties and use them in actual technologies. At this point, Denmark, and particularly the Copenhagen area, is among the world's leaders.

The awareness of the many applications of quantum technology is increasing not only among researchers but in society as a whole. Both Danish companies and public institutions are approaching the quantum-ready stage, actively working to exploit the possibilities of quantum technology, supported by research from DTU.

Three main fields of technology

The development of quantum technologies is taking place in several different fields. DTU is particularly engaged in three of them—quantum computing, quantum sensors, and quantum communication. This comprises the whole gamut from basic research, which is still necessary in virtually all areas of quantum technology, to actual technology development. Here, DTU especially plays a role in developing technologies for implementation and use by authorities and industry.

At the same time, awareness of the many applications is increasing in society as a whole, and both Danish companies and public institutions are approaching the quantum-ready stage, where they are actively working to exploit the possibilities of quantum technologies—supported by research from DTU, among others.

Contact our experts in quantum technology

Lydia Baril

Lydia Baril Head of Quantum DTU

Lydia Baril is head of DTU's center for quantum technology, Quantum DTU. Lydia Baril has broad international experience with research, start-ups and held management positions at companies within the industry, e.g. Microsoft's Quantum Lab. Quantum DTU is a joint gateway, spanning research, education and collaboration, as well as the development of quantum technology. Quantum DTU coordinate activities inside DTU but also in collaboration with companies, organizations and authorities.
Leif Katsuo Oxenløwe

Leif Katsuo Oxenløwe Professor, Group Leader

Leif Katsuo Oxenløwe is a professor at DTU and an expert in optical communication and optical signal processing. He conducts research in the development of new energy-efficient communication technologies and optical quantum technologies that can ensure both greater data capacity and increased cyber security. Leif Katsuo Oxenløwe has wide knowledge of quantum technology in the areas of quantum computers, quantum sensors, and especially quantum communication.
Jonas Schou Neergaard-Nielsen is an associate professor at DTU and an expert in quantum physics and quantum information technology. His research in experimental quantum optics is centered around the exploration of light with non-classical properties and its applications in quantum information. Jonas Schou Neergaard-Nielsen is knowledgeable about quantum sensors, quantum communication and particularly quantum computers.

FAQ

See our answers to frequently asked questions about quantum technology.

Quantum physics is the branch of physics that deals with matter, energy and interactions at the most fundamental level. Quantum mechanics is the theory that describes the phenomena of quantum physics.

Quantum technology is a collective term for several new technologies that utilize quantum physics to perform tasks that are impossible or cannot be done sufficiently precisely with conventional technologies.

The most talked about example of quantum technology is the quantum computer, which researchers and companies have been working on for approx. 30 years. Various versions of functioning quantum computers already exist, but the technology is far from mature enough to be able to solve relevant practical problems advantageously.

Other quantum technologies are closer to application in society. This concerns, among other things, technologies for quantum communication and quantum sensors, which DTU is also working on.

The superposition principle of quantum mechanics states that if two states |a> and |b> are possible states for a quantum physical system (such as quantum bits), the sum of the two is also possible. Simply put, the system can be simultaneously in two places or two states. One of the best-known examples of superposition is the thought experiment of Schrödinger's cat.

Entanglement means that two or more particles are connected so that their states depend on each other – regardless of distance. So even though they are physically separate, they are entangled in a common quantum state. If entangled particles are measured, there will be stronger agreement or - in a more technical term - correlation between the results than is possible for a classical physical system. Simply put, one atom knows what the other is doing.

A quantum computer is a processor without a screen and keyboard that utilizes quantum mechanical principles.

The basic unit in a quantum computer (a quantum bit) behaves differently to a bit in an ordinary computer. Where an ordinary computer uses bits (0 or 1) to store and process information, a quantum computer uses quantum bits – also called qubits – that can be in a so-called superposition, where it is 0 and 1 at the same time. It increases the number of possible calculations exponentially.

In principle, the computing power therefore increases exponentially with the number of quantum bits in a quantum computer, whereas the computing power of an ordinary computer simply increases linearly. This allows the quantum computer to perform special types of complex calculations that even the largest supercomputer will never be able to handle. 

In 2023, there are still no practically relevant applications of quantum computers that could not just as well be done by a supercomputer. 

But when the technology behind the quantum computer becomes more mature, and capable of solving the complex problems that a supercomputer cannot do, it is expected to be groundbreaking. For example, route planning in the transport industry can become much more accurate, which will both save time and reduce carbon emissions in the transport sector. It could also increase the utilization of sustainable energy sources such as wind and solar power.   

Consequently—while it was previously mainly interesting from a scientific perspective—companies, authorities, and investors have now increasingly been preparing themselves for the potential of quantum computers and the opportunities they offer. 


Researchers are working on developing different types of quantum computers. They are sorted according to the kind of qubits they use - such as:

  • Superconducting qubits are encoded in superconducting materials (which conduct electrical current without resistance). The quantum state is encoded in the current flowing through the circuit, can be manipulated with high precision and can be integrated into existing semiconductor circuits. The lifetime of superconducting qubits is relatively short. It is the most widespread technology used by, e.g. Google, IBM and Microsoft.
  • Trapped ion qubits use atoms or molecules with an electrical charge called ions. Electromagnetic fields capture and manipulate ions to store and process quantum information. An advantage of trapped ion qubits is that they are exact and can be kept longer than other qubits.
  • Cold atom qubits are produced using laser light to slow down atoms and cool them to very low temperatures. They are based on Bose-Einstein condensates, which is a state where an extremely cold gas of atoms condenses into one common quantum state and thus behaves as a unit. Cold atom qubits can achieve a long lifetime but are slow to manipulate.
  • Photonic qubits are qubits encoded in light. It can either be in single-photon or coherent light states. The technology uses well-established methods and techniques to control and manipulate optical quantum states. Additionally, integrated optics make it possible to produce photonic quantum processors at chip scale and thus scale the platform.
  • NV centres in diamonds are encoded in a diamond's nitrogen-vacancy (NV) centres. NV centres are defects in diamond crystals where a nitrogen atom replaces a carbon atom, and the crystal has an empty site. Their quantum state can be manipulated with high precision with laser light and electromagnetic fields. They can be long-lived and maintain their quantum state for longer than other qubits.

A standard computer calculates with bits that can either be 0 or 1. A quantum computer calculates with quantum bits (qubits), which can be in superpositions of 0 and 1. Simply put, qubits can be in two states simultaneously (see superposition). It increases the number of possible calculations exponentially for each qubit in the system.

Qubits are quantum systems and can be entangled (see entanglement). While the quantum computer is calculating, its qubits will generally be entangled.

By measuring the qubits, they "collapse" and become either 0 or 1. This gives a readable result of the calculation.

Qubits are very sensitive to disturbances – noise – from the environment, which can lead to errors in their state and, thus, in the calculation result. One of the significant challenges in making larger quantum computers is being able to correct errors.

In quantum simulation, controllable quantum systems simulate complex physical systems that are difficult or impossible to simulate on classical computers. This has applications in materials science, drug discovery and other fields.

Quantum algorithms can run on a quantum computer and exploit its unique properties to solve complex problems much faster than classical algorithms. Quantum algorithms may be used in developing new materials, cryptography, medicine, logistics, finance and many other fields.

Quantum ready refers to the fact that a company, organization or nation has adapted its infrastructure to implement and use future quantum technologies. It also means that they have become aware of the contexts in which quantum technologies can lead to a gain or improvement compared to existing technologies. Concerning data security, quantum ready also implies that they have taken precautions regarding securing their infrastructure against attacks from quantum computers.

Quantum Internet is a theoretical network that uses quantum principles to communicate and exchange information. If the quantum internet becomes a reality, it will offer a secure and reliable way to communicate and share information. It will also make it possible to connect quantum computers across large distances.

Quantum communication or quantum cryptography is a way to secure information using quantum mechanical principles.

It is necessary since quantum computers will probably be able to break all the algorithm-based encryption methods used today. Quantum communication can provide completely new opportunities for data security by encoding information in quantum states of light. As the quantum mechanical properties are being exploited, it is physically impossible to measure the light without disturbing the signal.  If someone tries to intercept the information being sent, the system will notice this change and disconnect.

A special type of quantum communication system is quantum key distribution (QKD). Here, the sender encodes information in quantum states of light, which is subsequently measured by the receiver. The fundamental randomness of quantum physical processes allows the two parties to generate a set of random numbers that only they know and of which it can be proven that no third party has knowledge. The set of numbers is used as the key for the encryption, which is symmetric and unbreakable. Therefore, only the sender and receiver have access to the information. 

The strength of quantum communication is that the sender and receiver can detect any attempt at listening in. This makes it possible to create a secure communication channel where you do not have to worry about eavesdropping or data being intercepted by an unauthorized party. Not even an upcoming quantum computer will be able to break the encryption, as there are no effective algorithms for breaking symmetric encryption.

Quantum communication thus addresses one of today’s most important cyber security challenges: creating secure communication channels in a world where eavesdropping and surveillance are common. Quantum communication is therefore expected to become a powerful tool in the protection of sensitive personal data or information of critical importance to society.

The ultimate goal is a ‘quantum internet’ for secure global communication and for the interconnection of quantum computers.

Quantum sensors use quantum mechanical effects to perform measurements that are far more accurate than those performed using conventional sensors. Sensors react to the physical world around them and are used to measure the intensity of light and other electromagnetic fields, sound, pressure, time, gravity, and much more. Quantum sensors are very sensitive and can measure much smaller quantities of material and show details in the studied material that are not visible using conventional measurement techniques.

Quantum sensors generally use quantum physical objects as part of the structure of the sensor. The sensors achieve their properties by controlling and manipulating the quantum physical properties of these objects and their interaction with their surroundings such as motion, acceleration, or electric and magnetic fields.

Quantum sensors are one of the most mature areas of quantum technology and are thus already being used. Their applications include:

  • Navigation based on measurement of magnetic fields—relevant if, for example, GPS is in risk of being jammed
  • Mapping of the subsoil—for example prior to construction or to find raw materials. 

The technology lacks development in some areas, but, in future, quantum sensors are expected to be used in, e.g., life science and for improved diagnosis of diseases by:

  • analysing biological tissue
  • measuring nerve impulses in, e.g., brain and muscle tissue
  • understanding the importance of quantum phenomena to biological processes.

Quantum materials are materials where the quantum physical properties play an essential role in their behaviour. These materials have unique electronic and magnetic properties that can be exploited in various technologies, from superconductivity to quantum computers.

Quantum computers can find the best solution among many options for complex problems such as logistics, planning and supply chain management. It can be of great importance in areas such as finance, production and transport, e.g. in connection with the optimization of route planning for logistics companies and the design of more efficient production processes.

Quantum DTU

Quantum DTU is DTU’s quantum technology centre. The centre is a point of access to the many researchers at DTU who work with different parts of quantum technology, from basic research to the application of the technology by companies and authorities. This comprises areas such as quantum sensors, quantum communication, encryption, quantum computers, etc.
Quantum DTU is also the basis for even greater collaboration between DTU and companies, authorities, and others that want to become - or already are - ’quantum ready’ and would like to benefit from DTU’s research and education.

Read more about Quantum DTU

Create the quantum technologies of the future

If you want to be a part of a scientific field with growing job opportunities and large investments worldwide, you might take a look at the MSc programme in Quantum Information Science. The programme is offered in English in a collaboration between the University of Copenhagen and DTU with admission at the University of Copenhagen. Quantum Information Science is an interdisciplinary education combining computer science, mathematics, and physics. It provides you with a comprehensive theoretical, technological, and experimental knowledge in the quantum field.

Read more about the MSc in Quantum Information Science

The history of quantum technology at DTU

It has been 100 years since Denmark was the international hub for the newly discovered theoretical quantum physics, and now DTU is at the forefront of developing new quantum technologies.

Follow the development through a series of historical highlights:

Articles about quantum technology

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