Quantum computing uses quantum mechanics to process information in ways that classical computers cannot. This post is the first in a series covering key milestones and state-of-the-art developments from 2019 onwards. As new breakthroughs arise, we’ll publish follow-up posts to keep track of the field’s evolution. This post summarizes the key milestones in the field up to 2019.

Early Quantum Theory

In 1900, Max Planck proposed that energy is quantized to explain blackbody radiation [1]. This idea led to the development of quantum mechanics. In 1926, Erwin Schrödinger formulated his wave equation to describe particle behavior [2], and in 1927, Werner Heisenberg introduced the uncertainty principle [3], showing limits on measuring certain pairs of properties simultaneously.

Classical Computation Foundations

Alan Turing’s 1936 paper defined the Turing machine as a model of computation using classical bits [4]. This framework established what problems are computable and set the stage for later comparisons with quantum models.

First Quantum Models

In 1968, Stephen Wiesner described using non‑orthogonal quantum states for secure communication [5]. Paul Benioff (1980) and Yuri Manin independently proposed quantum versions of the Turing machine [6]. In 1981, Richard Feynman pointed out that classical computers struggle to simulate quantum systems efficiently and suggested building quantum simulators [7].

Universal Quantum Computation

David Deutsch formalized the universal quantum computer in 1985, showing it could simulate any physical system [8]. Two landmark algorithms followed: Shor’s factoring algorithm (1994) demonstrated exponential speedup over classical methods [9], and Grover’s search algorithm (1996) provided a quadratic speedup for unstructured search [10].

Experimental Progress and NISQ

Early experiments used nuclear magnetic resonance (NMR) to manipulate a few qubits. Later, superconducting circuits and trapped ions allowed scaling to tens of qubits. D-Wave introduced a commercial quantum annealer in 2011 [11]. In 2016, IBM launched the IBM Quantum Experience, giving public access to a five-qubit processor and marking the start of the NISQ (Noisy Intermediate-Scale Quantum) era [12].

References

[1] Planck, M. (1900). On the Law of Distribution of Energy in the Normal Spectrum. Annalen der Physik, 4(3), 553-563.

[2] Schrödinger, E. (1926). Quantisierung als Eigenwertproblem. Annalen der Physik, 79(4), 361-376.

[3] Heisenberg, W. (1927). Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik. Zeitschrift für Physik, 43(3-4), 172-198.

[4] Turing, A. M. (1936). On Computable Numbers, with an Application to the Entscheidungsproblem. Proceedings of the London Mathematical Society, 42(1), 230-265.

[5] Wiesner, S. (1983). Conjugate coding. ACM SIGACT News, 15(1), 78-88.

[6] Benioff, P. (1980). The computer as a physical system: A microscopic quantum mechanical Hamiltonian model of computers as represented by Turing machines. Journal of Statistical Physics, 22(5), 563-591.

[7] Feynman, R. P. (1982). Simulating physics with computers. International Journal of Theoretical Physics, 21(6), 467-488.

[8] Deutsch, D. (1985). Quantum theory, the Church–Turing principle and the universal quantum computer. Proceedings of the Royal Society of London A, 400(1818), 97-117.

[9] Shor, P. W. (1994). Algorithms for quantum computation: discrete logarithms and factoring. In Proceedings 35th Annual Symposium on Foundations of Computer Science (pp. 124-134). IEEE.

[10] Grover, L. K. (1996). A fast quantum mechanical algorithm for database search. In Proceedings of the Twenty-Eighth Annual ACM Symposium on Theory of Computing (pp. 212-219).

[11] Johnson, M. W., et al. (2011). Quantum annealing with manufactured spins. Nature, 473(7346), 194-198.

[12] IBM Quantum Experience. (2016). IBM Quantum Platform. https://quantum-computing.ibm.com/