Microsoft Majorana

Microsoft announced Feb 19, 2025: Majorana 1 Explained: The Path to a Million Qubits, Microsoft’s Majorana 1 chip carves new path for quantum computing.

  • Qubits. Hard to make qubits sustainiable and reliable.
  • Ettore Majorana (1906-1938) topological state, allow us to scale millons qubits on a chip.

Topological quantum computing

  • Methods - 2-Level systems: Frequency of charge oscillation; Energy levels of an atom; Path photon takes; Number of photons; Electron spin or charge; Spin of an atom.

  • Method - Topological (Quasi) Qubit : made from many electrons working together (collective behaviour of electrons) - Marjorana zero mode / Marjorana particle, which a energy gap to protect qubit from noise.
    • Bit : odd or even number of electrons.
    • Need the right combination of materials, in the right shape, which is difficult. Building steps : (1) Material growth step; (2) Nanofabrication step.
    • The objective of the delicated fabrication is to make the marjorana particle pair separate, to protect the energy gap.

Quantum Computing

The Map of Quantum Computing - Quantum Computing Explained

  • Qubit - quantum wave function.
  • Entanglement : All the qubits entangled together, with N qubits, the number of possible states is $2^N$. A quantum computer is in all the super states at the same time.
  • Interference : quantum wavefunctions forms overall wavefunction, which reflects the probability distribution.
    • When computing : (1) use instructive interference to increase the probabilities of the correct answer; (2) use destructive interference to decrease teh probabilities of the incorrect answer.

Quantum Algorithms. Example: Shor's algorithm - factorisation of large number (used for encryption). Scale of log(N) ($2^{N/2}$ for classic computer), Quantum complexity theory.

Applications : Quantum simulation, Optimization, Machine Learning.

Models of quantum computing.

  • Universal methods (Mathematically equivalent):
    • Gate (Circuit) Model : apply gates, which rotating the qubit’s directions, to process algorithm.
    • Measurement based (on-way) Model.
    • Abiabatic Model : make the minmum energy state be the answer of the problem.
  • Quantum annealing : also energy minimization, but not universal.
  • Topological quantum computing : Majorana zero-mode quasi-particle. More stable, but not observed yet.

Physical realisations (2-Level systems).

  • Obstacles : Decoherence (entangled to environment); Noise; Scalability.
    • Quantum error correction (use a group of qubits).
  • Superconducting quantum computers.
  • Quantum dot quantum computers (Silicon spin quantum computers).
  • Linear optical quantum compters, light system.
  • Trapped ion quantum computers.
  • Colour center quantum cimputer : qubits embedded in materials.
  • Neutral atoms in optical lattices : trapped atoms in optical lattice, coolde to millionths of a kelvin.
  • Others : Electron-on-helium qubit, Cavity quantum electrodynamics, Magnetic molecule, Nuclear magnetic resonance.

Qiskit.org