A true universal quantum computer is a type of quantum computer that can solve a wide range of computational problems exponentially faster than classical computers. It utilizes the principles of quantum mechanics to manipulate quantum bits, or qubits, which can exist in superpositions of 0 and 1, as well as in entangled states. This enables quantum computers to perform parallel computations and potentially solve certain problems more efficiently than classical computers.
Quantum computers have the potential to revolutionize fields such as cryptography, optimization, material science, and drug discovery. They could provide exponential speedup for certain algorithms, such as Shor's algorithm for factoring large numbers, which has implications for breaking classical cryptographic protocols like RSA.
However, building a practical and reliable universal quantum computer is an immense scientific and engineering challenge. Quantum systems are extremely fragile and prone to noise and errors caused by interactions with the environment. Maintaining and controlling the delicate quantum states required for computation, known as quantum coherence, is a major obstacle.
Currently, we are in the early stages of quantum computing development. Quantum computers with a small number of qubits, known as noisy intermediate-scale quantum (NISQ) devices, have been demonstrated by several companies and research institutions. These devices have limited computational power and are susceptible to errors due to noise.
As for the timeline of achieving a true universal quantum computer, it is difficult to provide an exact estimate. The field of quantum computing is advancing rapidly, and there are significant research efforts and investments being made globally. However, there are still many technical challenges to overcome, such as improving qubit coherence, reducing errors, and developing error-correction techniques.
Some experts believe that it may take several decades to reach a stage where practical and fault-tolerant universal quantum computers become a reality. However, it's important to note that progress in quantum technologies is highly unpredictable, and breakthroughs could potentially accelerate the timeline.