quantum computer

History

In the 1980s, physicist Richard Feynman suggested that a quantum computer could more accurately simulate natural processes. David Deutsch developed the theory, and by the late 1990s, the first working devices were built.

How it works

Qubits are made from atoms, ions, or superconducting circuits. Their state is controlled by laser pulses or microwave radiation — analogous to the logic gates of a regular processor. Superposition allows processing many possibilities in one step, and interference (like wave addition) amplifies the desired result, which is then read out.

History

In the 1980s, physicist Richard Feynman suggested that a quantum computer could more accurately simulate natural processes. David Deutsch developed the theory, and by the late 1990s, the first working devices were built.

How it works

Qubits are made from atoms, ions, or superconducting circuits. Their state is controlled by laser pulses or microwave radiation — analogous to the logic gates of a regular processor. Superposition allows processing many possibilities in one step, and interference (like wave addition) amplifies the desired result, which is then read out.

History

The concept of quantum computing was independently proposed by Yuri Manin (1980) and Richard Feynman (1981). In 1985, David Deutsch created a model of a universal quantum computer. Shor's algorithm (1994) for factoring numbers attracted attention due to the threat to RSA encryption. Grover's algorithm (1995) accelerates search. Experiments evolved from 2-qubit NMR schemes to ion traps and superconducting qubits. In 2012, the Nobel Prize was awarded to Serge Haroche and David Wineland for the manipulation of individual quantum systems.

How it works

The evolution of the qubit state vector in Hilbert space is described by the Hamiltonian. The initial state (usually |0...0⟩) is sequentially transformed by unitary gates, which create superposition and entangle the qubits. Algorithms such as the quantum Fourier transform adjust the amplitudes so that interference amplifies the target state. Measurement yields one of the outcomes with probability |amplitude|². The no-cloning theorem guarantees that an unknown quantum state cannot be exactly copied, which is fundamental for protocol security.

Open problems & fun facts

Scaling the number of qubits while maintaining coherence (the decoherence problem); Error correction: achieving the threshold for fault-tolerant computation (error rate required less than ~10⁻³ per gate); Creating practical quantum algorithms that outperform classical ones for industrial tasks; Understanding the limits of quantum speedup and complexity classes (e.g., BQP vs NP)

💡 The D-Wave quantum computer (a Canadian company) uses quantum annealing, not the universal gate model, which sparks debates about its 'quantumness' and actual speedup, but its devices have already been purchased by several research laboratories.