Many academics and industry experts consider us to be living through a second quantum revolution. One of the largest developments to be undertaken in this revolution is the creating of the quantum computer. To understand the significance and advantages to creating a quantum computer, we need to take a look at the quantum physics which allows them to operate.
Many people who have not extensively studied quantum physics and who hear the word “quantum” believe it to imply something strange and unexplainable is happening. For those of us who have studied quantum mechanics this viewpoint can be dangerously close to the truth sometimes. In a simple statement, quantum mechanics describes the physics of very small objects such as electrons, protons and the atoms they make up. Among the types of behaviours we are presented with in quantum physics we have quantum superposition and quantum entanglement as two of the most of important. Quantum superposition means a quantum object can exist is a superposition of possible states with a given probability. An example of this is found when considering the spin of an electron. Spin is a quantum behaviour analogous to the rotation of the Earth around its own axis and we can take it to be pointing upwards(spin up), or downwards(spin down). Until we measure it, the electron actually exists in a superposition of spin up and spin down with us(the observers) unable to precisely say what state the electron is actually in. Quantum entanglement is a concept which confused great minds such as Einstein. If we have two quantum objects which are linked with each other(entangled) it means that any action we perform on one of the objects, will directly influence the behaviour of the other even if nothing is done to it. Returning to the electron spin example, if we now have two electrons which are entangled with a 50-50 chance of measuring spin up or spin down on a single electron we can observe the phenomena of entanglement. First, the electrons are separated by a massive distance which light cannot even travel instantaneously. Next, a measurement is performed on the first electron and the outcome is spin up. This guarantees that the second electron is in a spin down state and the same holds for opposite measurement outcomes. Through entanglement we were able to characterise the state of our entire system through the measurement of one piece of it, and also have this outcome transmitted over an unimaginable distance instantaneously.
It’s clear looking the behaviour seen in our everyday macroscopic world that these sorts of phenomena do not fit in and appear illogical. However as illogical and counter-intuitive as they may be, they have been found to be quite practical and useful as it turns out. In this era of the second quantum revolution we have progressed from discovering these behaviours to studying how to make use of them. Such a use is in the development of quantum technology, with a large focus on quantum computers.
A generic image related to computation would be a large block of 0’s and 1’s which constitute the bits of a computer and exist as 0 or 1. In quantum computers we have qubits(quantum bits or two level quantum systems) which can use quantum superposition to exist in both the 0 and 1 state at the same time. This property along with entanglement between qubits allows for faster information processing capabilities in quantum computers than in classical computers. In today’s research being carried out by university academics and in industry the focus is on how to get more qubits into quantum computers so they are prepared to tackle large scale problems where they will provide an advantage what is possible with classical supercomputers. This is being done by looking at decoherence effects between qubits as well as creating quantum algorithms which provide a clear advantage as to how quantum computers will outperform classical computers on particular problems.
We now know the basic operation principles of a quantum computer and where their development is currently at, but the question of where they will be used in the future still remains.
Any quantum problem: Quantum computers, naturally, are better suited to simulating quantum related behaviour. This has clear benefits for researchers studying quantum physics and quantum chemistry but has benefits beyond those fields as well. Molecular structure and configuration rely on quantum mechanics and can be better modelled using quantum simulation techniques. This ability to unlock more complex properties of molecules means quantum computers will accelerate progress in materials synthesis and drug development by bioengineers.
Cryptography: While quantum computers could pose a threat to modern day encryption techniques through ideas such as Shor’s algorithm, the sensitivity and uncertainty in quantum systems could allow for new quantum based encryption schemes to be developed.
Database Searching: There are many operation today which require the processing of large amounts of data and searching databases containing this information. This is a task which is known to be more efficient on quantum computers through the application of Grover’s algorithm. There is benefits to be found in manufacturing operations and in data-processing for the development of Artificial Intelligence through this advantage of using quantum computers.
These are only examples of the tasks which are aimed to be tackled in the future using larger scale quantum computers. The second quantum revolution also is not solely focused on the development of quantum computers with other technology such as quantum sensors a very topical focus of research as well. It will be interesting how this technology is improved and applied in the coming years.