Depending on the individual you ask, it is believed that quantum computers could either lead to the breaking of the internet, making almost all data security protocols obsolete, or provide a solution to the climate crisis through computational power. These powerful devices, which utilize the properties of quantum mechanics, are currently a topic of much discussion. In the previous month, IBM unveiled its latest quantum computer, Osprey, a new 433 qubit processor that is three times more powerful than its 2021 predecessor.
Although quantum computers have limitations and cannot solve all problems, they are still groundbreaking in their potential. The field of quantum science studies the physical properties of nature on the scale of atoms and subatomic particles. Supporters of quantum technology believe that it could lead to significant advancements in fields such as drug discovery and materials science. This presents the exciting prospect of developing lighter and more efficient electric vehicle batteries or materials that could effectively capture CO2.
Considering the looming climate crisis, technology with the potential to solve complex issues such as these is bound to attract significant attention. It is, therefore, no surprise that some of the largest tech companies in the world, including Google, Microsoft, Amazon, and IBM, are heavily investing in it and positioning themselves for a quantum future.
How do quantum computers work?
The machines that are attracting so much interest have a utopic-sounding quality to them. Therefore, it might be useful to comprehend their workings and how they differ from classical computing.
To start, consider every device currently available, ranging from smartphones to supercomputers. All of these devices have always operated on the same binary code principle.
In essence, the chips in our computers contain tiny transistors that function as on/off switches, representing the two possible values of 0 or 1, known as bits. These bits can be grouped together into more complex units, forming long strings of 0s and 1s that carry encoded data commands, instructing the computer on what to do, such as displaying a video, playing an mp3 file, or allowing you to type an email.
However, a quantum computer functions entirely differently. Instead of bits, the basic unit of information in quantum computing is a quantum bit, or qubit, which is typically a subatomic particle such as an electron or photon.
The advanced computational power of a quantum machine lies in its ability to manipulate these qubits. A qubit is a two-level quantum system that enables quantum information storage.
Superposition
Superposition in qubits refers to the property that a qubit can be in a linear combination of the two classical states, 0 and 1. Specifically, a qubit can be expressed as a superposition of the basis states |0⟩ and |1⟩ as follows:
|ψ⟩ = α|0⟩ + β|1⟩
where α and β are complex amplitudes, and the squared magnitudes of the amplitudes |α|² and |β|² represent the probabilities of measuring the qubit in the states |0⟩ and |1⟩, respectively.
To clarify, in contrast to a classical bit that can only be in one of the two states, 0 or 1, a qubit in superposition can exist in both states simultaneously, which is often referred to as a “quantum superposition.” Therefore, a qubit can be represented as a linear combination of both states, where the probability of observing the qubit in either state depends on the magnitudes and phases of the complex amplitudes.
An analogy often used to explain quantum superposition is that of a penny. When a penny is not moving, it has only two possible outcomes, heads or tails. However, when it is tossed or spun, it can exist in a superposition of both states simultaneously until it lands and a measurement is made, collapsing the superposition to one of the classical states.
The ability to be in multiple states at once allows quantum computers to encode data using exponentially more states than classical computers, which are limited to only two states. This property of quantum systems is what gives quantum computers their potential for exponential speedup in certain computational tasks.
Quantum entanglement
The phenomenon of entanglement is a crucial property that underpins the workings of quantum computing. It is a mysterious feature of quantum mechanics, which even Einstein found puzzling, referring to it as “spooky action at a distance”. When two qubits are created in an entangled state, there is a direct and measurable correlation between their behavior, no matter how far apart they are. This correlation does not have an equivalent in the classical world.
The importance of entanglement lies in its ability to create a much stronger connectivity between the different units and qubits of a quantum computer. This results in a more powerful and efficient system than a classical computer. As explained by Alessandro Curioni, director of the IBM Research Lab in Zurich, “This property of entanglement is very important because it brings a much, much stronger connectivity between the different units and qubits. So the elaboration power of this system is stronger and better than the classical computer.”
In recognition of their contributions to the field of quantum information, the Nobel Prize for physics was awarded this year to three scientists: Alain Aspect, John Clauser, and Anton Zeilinger. Their experiments on entanglement helped to advance the field and demonstrate the potential of quantum computing.
Why do we need quantum computers?
To put it simply, quantum computers work by using the principles of quantum mechanics to manipulate quantum bits (qubits) instead of classical bits. This allows quantum computers to perform certain tasks much more efficiently than classical computers, particularly in the simulation of the physical and quantum world.
One area where quantum computers could be particularly useful is in the design and discovery of new materials with specific properties. However, there is also a concern that the immense calculation power of quantum computers could break the encryption protocols that currently secure the internet.
To address this concern, it is recommended that organizations and state actors update their cryptography to quantum-safe algorithms that cannot be broken by quantum computers. While this may have a negative impact on existing data that hasn’t been encrypted with quantum-safe algorithms, it is still important to prepare for the potential impact of quantum computers on encryption.
Ultimately, while quantum computers have the potential to bring significant benefits in certain areas, it is important to be aware of their potential impact on security and privacy, and take appropriate steps to mitigate these risks.
