Quantum Computating & Qiskit
A quantum (plural quanta) is the minimum amount of any physical entity (physical property) involved in an interaction.
Quantum mechanical properties
Superposition
Superposition refers to a combination of states we would ordinarily describe independently. To make a classical analogy, if you play two musical notes at once, what you will hear is a superposition of the two notes.
Entanglement
Entanglement is a famously counter-intuitive quantum phenomenon describing behavior we never see in the classical world. Entangled particles behave together as a system in ways that cannot be explained using classical logic.
Interference
Finally, quantum states can undergo interference due to a phenomenon known as phase. Quantum interference can be understood similarly to wave interference; when two waves are in phase, their amplitudes add, and when they are out of phase, their amplitudes cancel.
Walking the history
The Uncertainty Principle
German physicist Werner Heisenberg introduces the uncertainty principle, which asserts that you can’t know everything about a quantum particle at the same time. The more you know about its position, the less you know about its momentum, and vice versa.
Shor factor algorithm
MIT’s Peter Shor shows that it’s possible to factor a number into its primes efficiently on a quantum computer — a problem that takes classical computers “an exponentially long time” to solve for large numbers. His algorithm launches an explosion of theoretical and experimental interest in the field of quantum computing.
Quantum Error Correction
Quantum error correction emerges from several groups around the world. The theory shows that it’s possible to use a subtle redundancy to protect against environmental noise, making the physical realization of quantum computing significantly more tenable.
DiVincenzo Criteria
Researcher David DiVincenzo outlines five minimal requirements for creating a quantum computer: (1) a well-defined scalable qubit array; (2) an ability to initialize the state of the qubits to a simple fiducial state; (3) a “universal” set of quantum gates; (4) long coherence times, much longer than the gate-operation time; (5) single-qubit measurement.
Topological Codes
The first topological quantum error correcting code, known as the surface code, is proposed by California Institute of Technology professor Alexei Kitaev. The surface code is currently considered the most promising platform for realizing a scalable, fault-tolerant quantum computer.
Experimentally Factoring
Shor’s algorithm is demonstrated for the first time in a real quantum computing experiment, albeit with a very pedestrian problem: 15=3x5. The IBM system employed qubits in nuclear spins, similar to an MRI machine.
Circuit QED
Robert Schoelkopf and his collaborators at Yale University invent circuit QED, a means of studying the interaction of a photon and an artificial quantum object on a chip. Their work established the standard for coupling and reading out superconducting qubits as systems continue to scale.
Transmon Superconducting Qubit
Schoelkopf and his collaborators invent a type of superconducting qubit designed to have reduced sensitivity to charge noise, a major obstacle for long coherence. The superconducting qubit has been adopted by many superconducting quantum groups.
Coherence Time Improvement
Several important parameters for quantum information processing with transmon qubits are improved. IBM extends the coherence time, which is the duration that a qubit retains its quantum state, up to 100 microseconds.
[[2,0,2]] Code
With a single quantum state stabilized, it’s possible to detect both types of quantum errors: bit-flips and phase-flips. The code is realized in a 4-qubit lattice arrangement, which serves as a building block for future quantum computing systems.
Breaking the Simulation Barrier
On October 19, Science published “Quantum Advantage with Shallow Circuits” – a significant mathematical result –a formula –that will guide the development of future quantum algorithms. It’s a solid and necessary brick in the foundation of quantum computing. The formula stands apart because unlike Shor’s algorithm, it proves that a quantum computer can always solve certain problems in a fixed number of steps, no matter the increased input. While on a classical computer, these same problems would require an increased number of steps as the input increases.