1970s
- 1970 – Stephen Wiesner invents conjugate coding.
- 1973 – Alexander Holevo publishes a paper showing that n qubits cannot carry more than n classical bits of information (a result known as "Holevo's theorem" or "Holevo's bound"). Charles H. Bennett shows that computation can be done reversibly.
- 1975 – R. P. Poplavskii publishes "Thermodynamical models of information processing" (in Russian), Uspekhi Fizicheskikh Nauk,115:3, 465–501 which showed the computational infeasibility of simulating quantum systems on classical computers, due to the superposition principle.
- 1976 – Polish mathematical physicist Roman Stanisław Ingarden publishes a seminal paper entitled "Quantum Information Theory" in Reports on Mathematical Physics, vol. 10, 43–72, 1976. (The paper was submitted in 1975.) It is one of the first attempts at creating a quantum information theory, showing that Shannon information theory cannot directly be generalized to the quantum case, but rather that it is possible to construct a quantum information theory, which is a generalization of Shannon's theory, within the formalism of a generalized quantum mechanics of open systems and a generalized concept of observables (the so-called semi-observables).
Read more about this topic: Timeline Of Quantum Computing