Quantum computing
The machines that make post-quantum cryptography necessary: how they work, the companies building them, and an honest look at what today's quantum computers can and cannot do.
22 entries
- D-WaveD-Wave Systems sold the first commercial quantum computer in 2011 and builds quantum annealers for optimization, not universal gate-model machines.
- Google Quantum AIGoogle Quantum AI builds superconducting processors; its 2019 Sycamore supremacy claim was contested, and 2024 Willow showed below-threshold error correction.
- IBM QuantumIBM Quantum builds superconducting transmon processors, from the 127-qubit Eagle to the 1121-qubit Condor, and develops the Qiskit software stack.
- IonQIonQ builds trapped-ion quantum computers with all-to-all qubit connectivity, reports an algorithmic-qubits metric, and offers access through major clouds.
- Microsoft Azure QuantumMicrosoft Azure Quantum is a cloud platform for quantum hardware and software, paired with Microsoft's long-running topological-qubit research program.
- Neutral-atom qubitsNeutral-atom qubits hold single atoms in optical tweezer arrays and entangle them via Rydberg interactions, giving large, reconfigurable qubit registers.
- NISQ (Noisy Intermediate-Scale Quantum)NISQ, Noisy Intermediate-Scale Quantum, is John Preskill's 2018 term for today's noisy, uncorrected quantum machines holding dozens to hundreds of qubits.
- PasqalPasqal, based in France, builds neutral-atom quantum computers that use optical tweezers and Rydberg atoms for both analog and digital operation.
- Photonic quantum computingPhotonic quantum computing encodes qubits in photons and processes them with linear optics and measurement, near room temperature but limited by photon loss.
- PsiQuantumPsiQuantum pursues photonic quantum computing in silicon, manufacturing with GlobalFoundries, and states a goal of a fault-tolerant million-qubit machine.
- QuantinuumQuantinuum formed in 2021 from Honeywell and Cambridge Quantum and builds trapped-ion H-series processors known for gate fidelity and quantum-volume records.
- Quantum advantageQuantum advantage is a quantum computer beating the best classical methods on a task; useful advantage on practical problems is still limited as of early 2026.
- Quantum annealingQuantum annealing is a heuristic that encodes an optimization problem as an Ising Hamiltonian and evolves toward a low-energy state to find good solutions.
- Quantum circuitA quantum circuit is a sequence of quantum gates and measurements acting on qubits; it is the standard model in which quantum algorithms are expressed and run.
- Quantum error correctionQuantum error correction builds reliable logical qubits from many noisy physical qubits, using redundancy to suppress errors below a critical threshold.
- Quantum logic gateA quantum logic gate is a reversible unitary operation on qubits; small universal gate sets approximate any quantum computation to arbitrary accuracy.
- Quantum teleportationQuantum teleportation transfers an unknown quantum state using shared entanglement and two classical bits; it moves no matter and is not faster-than-light.
- Rigetti ComputingRigetti Computing is a full-stack superconducting quantum company that designs and fabricates its own chips and runs the Quantum Cloud Services platform.
- Superconducting qubitsSuperconducting qubits are circuits using Josephson junctions as artificial atoms, cooled to millikelvin, with fast gates but limited coherence times.
- Topological qubitsTopological qubits would store information nonlocally in states like Majorana zero modes, protecting it from local noise, but remain unproven as of early 2026.
- Trapped-ion qubitsTrapped-ion qubits store quantum information in electronic states of ions held in electromagnetic traps, giving high gate fidelity and all-to-all connectivity.
- XanaduXanadu, a Canadian company, builds photonic quantum computers and reported a 2022 Borealis quantum-advantage result in Nature; it maintains PennyLane.