The Four Pillars of Quantum

Classical computers use "Bits" that are either ON (1) or OFF (0). Quantum computers use "Qubits" (Quantum Bits), which follow four mind-bending rules of physics to unlock exponential processing speed.

1. Superposition

If you put a coin on a table, it is either Heads or Tails. That represents a standard Bit. But if you spin that same coin, what is it? While it is spinning, it exists as a blur of Heads and Tails at the exact same time. This state allows quantum computers to analyze millions of possibilities simultaneously, rather than sequentially (Preskill, 2018).

2. Entanglement

Imagine two magic dice. If you roll them in different rooms, they will always land on the exact same number, no matter the distance between them. In physics, this phenomenon is called Entanglement. If we connect two Qubits, altering the state of one instantly alters the other. This creates a deeply interconnected system capable of processing speeds we can barely comprehend (Einstein et al., 1935).

3. Interference

Much like how noise-canceling headphones function, quantum computers can create waves of probabilities that crash into each other. They use interference to deliberately cancel out all the incorrect answers and amplify the correct answer. Without this, a quantum computer would just generate random noise instead of a readable solution (Nielsen & Chuang, 2010).

4. Decoherence

Qubits are incredibly fragile, akin to a delicate house of cards. If the quantum processor gets too warm, or if there is even a microscopic magnetic vibration in the environment, the quantum state collapses back into standard 1s and 0s, destroying the calculation. Minimizing this noise is currently the biggest challenge in hardware engineering today (Schlosshauer, 2019).

Classical vs. Quantum

Feature
Classical Computers
Quantum Computers
Data Unit
Bit (Strictly 0 or 1)
Qubit (A spinning coin of 0 and 1)
Processing Method
Sequential (One calculation at a time)
Superposition (Multiple calculations at once)
Speed
Checks passwords one by one
Checks all passwords instantly

References

Note: The following articles can be accessed via the University of East London (UEL) Library Search or institutional login.

  • Einstein, A., Podolsky, B. and Rosen, N., 1935. Can quantum-mechanical description of physical reality be considered complete?. Physical Review, 47(10), p.777. [DOI Link]
  • Nielsen, M.A. and Chuang, I.L., 2010. Quantum computation and quantum information. Cambridge university press.
  • Preskill, J., 2018. Quantum computing in the NISQ era and beyond. Quantum, 2, p.79. [DOI Link - Open Access]
  • Schlosshauer, M., 2019. Quantum decoherence. Physics Reports, 831, pp.1-57. [DOI Link]