Timeline
From quanta to qubits
A century and a quarter separates Planck's quanta from the first error-corrected logical qubits. Physics supplied the paradoxes, mathematics the language, and computer science the question: what could be computed with all this? Filter by chapter to follow each thread.
1900 – 1934
The quantum revolution
Energy comes in packets, particles behave like waves, and in barely a decade the theory acquires its definitive mathematical form: vectors in Hilbert spaces.
-
1900
Planck's quanta
Max Planck
To explain the radiation of hot bodies, Planck assumes that energy is exchanged in discrete packets.
Chapter 01 · Qubits → -
1905
The photon
Albert Einstein
Light itself comes in quanta: the explanation of the photoelectric effect, which earned Einstein the Nobel Prize.
Chapter 01 · Qubits → -
1922
The Stern–Gerlach experiment
Otto Stern, Walther Gerlach
Silver atoms in a magnetic field split into exactly two beams: the first measurement of a qubit.
Chapter 03 · Measurement → -
1925
Matrix mechanics
Werner Heisenberg, Max Born, Pascual Jordan
Observable quantities are represented by matrices that do not commute.
Chapter 03 · Measurement → -
1926
Schrödinger's equation and Born's rule
Erwin Schrödinger, Max Born
The wave function evolves linearly; its squared modulus gives probabilities.
Chapter 02 · Interference → -
1927
The uncertainty principle
Werner Heisenberg
Position and momentum cannot both have sharp values. Robertson proves the general version in 1929.
Chapter 03 · Measurement → -
1927
Electrons that interfere
Clinton Davisson, Lester Germer
Electrons scattered by a crystal produce an interference pattern: matter behaves like a wave.
Chapter 02 · Interference → -
1932
Hilbert spaces
John von Neumann
Mathematische Grundlagen der Quantenmechanik gives the theory its rigorous form: states are vectors, observables are operators.
Chapter 01 · Qubits →
1935 – 1979
Paradoxes and information
Entanglement goes from an embarrassing paradox to a testable inequality, while information theory discovers that computing has a physical cost.
-
1935
EPR and entanglement
Albert Einstein, Boris Podolsky, Nathan Rosen; Erwin Schrödinger
Einstein argues that quantum mechanics is incomplete; Schrödinger names the phenomenon Verschränkung, entanglement.
Chapter 04 · Entanglement → -
1937
Boolean circuits
Claude Shannon
A master's thesis shows that relay circuits obey Boole's algebra: the birth of digital logic.
Chapter 00 · Bits → - 1939
-
1946
The Bloch sphere
Felix Bloch
To describe nuclear magnetic resonance, Bloch represents the state of a spin as a vector on a sphere.
Chapter 01 · Qubits → -
1948
The sum over paths
Richard Feynman
The amplitude of a process is the sum of the amplitudes of all the paths that lead to it.
Chapter 02 · Interference → -
1961
Landauer's principle
Rolf Landauer
Erasing a bit dissipates at least of heat: information is physical.
Chapter 00 · Bits → -
1964
Bell's theorem
John Bell
No local hidden-variable theory can reproduce all the predictions of quantum mechanics.
Chapter 04 · Entanglement → -
1969
The CHSH inequality
John Clauser, Michael Horne, Abner Shimony, Richard Holt
A version of Bell's inequality that can be tested in the laboratory with photons.
Chapter 04 · Entanglement → -
1973
Reversible computation
Charles Bennett
Every computation can be done without erasing information, and therefore without Landauer's cost.
Chapter 00 · Bits → -
1973
The Holevo bound
Alexander Holevo
qubits cannot transmit more than classical bits of information.
Chapter 01 · Qubits → -
1977
RSA
Ron Rivest, Adi Shamir, Leonard Adleman
Public-key cryptography based on the difficulty of factoring.
Chapter 07 · Shor's algorithm →
1980 – 1993
The idea of a quantum computer
Feynman proposes simulating nature with quantum machines, Deutsch defines the universal quantum computer and the first problems with a quantum advantage appear.
-
1980
Toffoli gate and quantum Turing machines
Tommaso Toffoli; Paul Benioff
A universal reversible gate, and the first model of a computer obeying quantum mechanics.
Chapter 00 · Bits → -
1980
The Tsirelson bound
Boris Tsirelson
Quantum correlations can reach, but not exceed, in the CHSH game.
Chapter 04 · Entanglement → -
1981
“Simulating physics with computers”
Richard Feynman
In a lecture at MIT (published in 1982), Feynman argues that simulating quantum systems requires computers that are themselves quantum.
Chapter 05 · Gates and circuits → -
1982
Aspect's experiments
Alain Aspect, Jean Dalibard, Gérard Roger
Entangled photons violate Bell's inequality with polarizers switched during the flight.
Chapter 04 · Entanglement → -
1982
The no-cloning theorem
William Wootters, Wojciech Zurek; Dennis Dieks
An unknown quantum state cannot be copied.
Chapter 03 · Measurement → -
1984
BB84
Charles Bennett, Gilles Brassard
The first quantum key distribution protocol: an eavesdropper cannot copy qubits without disturbing them.
Chapter 03 · Measurement → -
1985
The universal quantum computer
David Deutsch
Deutsch defines a quantum Turing machine able to simulate any physical process, and gives the first problem with a quantum advantage.
Chapter 05 · Gates and circuits → -
1989
One electron at a time
Akira Tonomura and colleagues
The double-slit experiment with single electrons: the interference pattern builds up dot by dot.
Chapter 02 · Interference → -
1992
The Deutsch–Jozsa algorithm
David Deutsch, Richard Jozsa
One query decides with certainty whether a function is constant or balanced.
Chapter 05 · Gates and circuits → -
1993
BQP and the Bernstein–Vazirani problem
Ethan Bernstein, Umesh Vazirani
The foundations of quantum complexity theory: the class BQP and the first superpolynomial oracle separations.
Chapter 06 · Quantum Fourier transform → -
1993
Quantum teleportation
Charles Bennett and colleagues
A Bell pair and two classical bits transfer an unknown qubit.
Chapter 04 · Entanglement →
1994 – 1999
Algorithms and codes
Six extraordinary years: Shor's and Grover's algorithms, the first error-correcting codes, the threshold theorem and the first qubits in the laboratory.
-
1994
Simon's algorithm
Daniel Simon
An exponential separation against randomized classical algorithms, for a periodicity problem. It inspires Shor.
Chapter 06 · Quantum Fourier transform → -
1994
Shor's algorithm
Peter Shor
Factoring and discrete logarithms in polynomial time on a quantum computer. The field explodes.
Chapter 07 · Shor's algorithm → -
1995
The first quantum code
Peter Shor
Nine physical qubits protect one logical qubit against any single-qubit error.
Chapter 09 · Errors and decoherence → -
1995
Ion-trap gates
Ignacio Cirac, Peter Zoller; Christopher Monroe, David Wineland
A proposal for quantum gates with trapped ions and, that same year, the first experimental two-qubit gate.
Chapter 05 · Gates and circuits → -
1995
Phase estimation
Alexei Kitaev
A general framework for quantum algorithms that estimate eigenvalues.
Chapter 06 · Quantum Fourier transform → -
1996
Grover's algorithm
Lov Grover
Unstructured search with queries instead of .
Chapter 08 · Grover's algorithm → -
1996
The Steane code
Andrew Steane
A seven-qubit code built from a classical Hamming code.
Chapter 09 · Errors and decoherence → -
1997
Search cannot be faster
Charles Bennett, Ethan Bernstein, Gilles Brassard, Umesh Vazirani
Any quantum search algorithm needs queries: Grover's is optimal.
Chapter 08 · Grover's algorithm → -
1997
The threshold theorem
Dorit Aharonov, Michael Ben-Or; Alexei Kitaev; Emanuel Knill, Raymond Laflamme, Wojciech Zurek
Below a constant error rate, arbitrarily long quantum computations are possible.
Chapter 09 · Errors and decoherence → -
1998
The Gottesman–Knill theorem
Daniel Gottesman, Emanuel Knill
Clifford circuits, however entangled, can be simulated efficiently by a classical computer.
Chapter 05 · Gates and circuits → -
1999
A superconducting qubit
Yasunobu Nakamura, Yuri Pashkin, Jaw-Shen Tsai
Coherent control of a qubit made from a superconducting electrical circuit, the technology of today's largest processors.
Chapter 05 · Gates and circuits →
2000 – 2017
Building qubits
Nuclear magnetic resonance, trapped ions, superconducting circuits, photons: a slow engineering race towards more qubits with fewer errors.
-
2000
DiVincenzo's criteria
David DiVincenzo
Five requirements for building a quantum computer, from scalable qubits to long coherence times.
Chapter 09 · Errors and decoherence → -
2001
15 = 3 × 5
Lieven Vandersypen, Isaac Chuang and colleagues (IBM)
Shor's algorithm factors 15 with seven nuclear spins in a molecule.
Chapter 07 · Shor's algorithm → -
2012
“Quantum supremacy”
John Preskill
Preskill coins the term for the point at which a quantum computer does something no classical one can do in a reasonable time.
Chapter 05 · Gates and circuits → -
2015
Bell without loopholes
Groups in Delft, Vienna and Boulder
Three experiments close the main loopholes of Bell tests at the same time.
Chapter 04 · Entanglement → -
2016
Quantum computing in the cloud
IBM
A five-qubit processor becomes available to anyone over the internet.
Chapter 05 · Gates and circuits →
2018 – today
From NISQ to fault tolerance
Noisy processors with dozens to hundreds of qubits, the first claims of quantum advantage and, finally, error correction below the threshold.
-
2018
The NISQ era
John Preskill
Noisy intermediate-scale quantum: useful processors before error correction?
Chapter 09 · Errors and decoherence → -
2019
Sycamore
Google AI Quantum and collaborators
53 superconducting qubits sample random circuits in 200 seconds, a task estimated to be extremely costly for classical supercomputers (an estimate later reduced by better classical algorithms).
Chapter 05 · Gates and circuits → -
2020
Jiuzhang
Jian-Wei Pan, Chao-Yang Lu and colleagues (USTC)
A photonic quantum advantage experiment based on the interference of dozens of photons (boson sampling).
Chapter 02 · Interference → -
2022
Nobel Prize for entanglement
Alain Aspect, John Clauser, Anton Zeilinger
For experiments with entangled photons that established the violation of Bell inequalities and pioneered quantum information science.
Chapter 04 · Entanglement → -
2023
Dozens of logical qubits
Dolev Bluvstein, Mikhail Lukin and colleagues
A neutral-atom processor runs algorithms on up to 48 error-detected logical qubits.
Chapter 09 · Errors and decoherence → -
2024
Post-quantum standards
NIST
FIPS 203, 204 and 205: the first standards for cryptography designed to resist quantum computers.
Chapter 07 · Shor's algorithm → -
2024
Below threshold
Google Quantum AI and collaborators
On the Willow processor, the logical error of a surface code halves each time its distance increases: the threshold theorem, seen in the laboratory.
Chapter 09 · Errors and decoherence → -
2025
RSA-2048 with under a million qubits
Craig Gidney
A new resource estimate lowers the cost of breaking RSA-2048 to less than a million noisy qubits running for under a week.
Chapter 07 · Shor's algorithm → -
2025
Nobel Prize for superconducting circuits
John Clarke, Michel Devoret, John Martinis
For the discovery of macroscopic quantum tunnelling and energy quantization in an electric circuit, the physics behind superconducting qubits.
Chapter 05 · Gates and circuits →