First experimental evidence that quantum computers are an advantage over conventional ones

First experimental evidence that quantum computers are an advantage over conventional ones
Arrangement of IBM's four-bit quantum superconducting device. / IBM Research

Quantum computers offer advantages over conventional computers, as demonstrated by scientists from IBM and the Technological Universities of Munich (Germany) and Waterloo (Belgium), who have found conclusive evidence for this claim for the first time.

The team developed a new quantum circuit that can solve a  specific difficult algebraic problem , but which has a simple structure: it only performs a fixed number of operations in each qubit. It is said that such a circuit has a constant depth.

In his work, published in Science, the researchers prove that the problem in question can not be solved using classic circuits of constant depth. In addition, they answer the question of why the quantum algorithm defeats any comparable classical circuit: the quantum algorithm exploits the non-locality of quantum physics: an interlaced state whose parts become separated over time.

Prior to this work, the advantage of quantum computers had not been tested or demonstrated experimentally, despite evidence pointed in this direction. An example of this evidence is Shor’s quantum algorithm, which efficiently solves the problem of prime factorization.

However, it is simply a theoretical conjecture of complexity that this problem can not be solved efficiently without quantum computers. It is also possible that the correct approach for classical computers has simply not been found.

Principal investigator Robert König, a professor of complex quantum systems theory at the Technological University of Munich, considers the new results mainly as a contribution to the theory of complexity: “Our result shows that quantum information processing actually provides benefits, without have to rely on theoretical conjectures of unproven complexity, “he says in a statement.

Beyond this, work provides new milestones on the road to quantum computers. Due to its simple structure, the new quantum circuit is a candidate for a short-term experimental realization of quantum algorithms.

Why are quantum computers faster?

The conventional ones obey the laws of classical physics, based on the binary numbers 0 and 1. These numbers are stored and used for mathematical operations. In conventional memory units, each bit, the smallest information unit, is represented by a microscopic point on a microchip. Each of these points can contain a load that determines whether the bit is set to 1 or 0.

In a quantum computer, however, a bit can be 0 and 1 at the same time. This is because the laws of quantum physics allow electrons to be in multiple places at the same time. Quantum bits, or qubits, therefore exist in multiple overlapping states.

This putative overlay allows quantum computers to perform operations on many values ​​at once, while a single conventional computer typically must execute these operations sequentially. The promise of quantum computing lies in the ability to solve certain problems significantly faster.

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