Quantum Computation: A Single Qubit's Infinite Possibilities

Amith2006
Messages
416
Reaction score
2
A qubit state can be represented geometrically by Bloch sphere. A Bloch sphere has infinite points and so a single qubit can represent infinite number of states. Qubit state is represented by,
Ipsi> = cos(theta/2)I0> + exp(i(phi))sin(theta/2)I1>
It is said in the Book on Quantum Computation by Nielsen & Chuang that u can store an infinite text on a single qubit in the infinite binary expansion of theta. How is that possible? Though a single qubit can be in anyone of the infinite number of states, how can it represent all the states at the same time? I can understand infinite expansion of theta but what do they mean by infinite binary expansion of theta?
 
Physics news on Phys.org
You know the "infinite number of states" are just superpositions of two states, yes?
Amith2006 said:
how can it represent all the states at the same time?
It can't, it is in TWO states at the same time, it is ONE of an infinite number of superpositions.

Amith2006 said:
How is that possible?

Just imagine theta written out in binary. It is an infinitely long binary string. You can store whatever you want on that string, and infinitely long text for example.
(the downside being that there is absolutely no way to recover it)
 
I am not sure if this belongs in the biology section, but it appears more of a quantum physics question. Mike Wiest, Associate Professor of Neuroscience at Wellesley College in the US. In 2024 he published the results of an experiment on anaesthesia which purported to point to a role of quantum processes in consciousness; here is a popular exposition: https://neurosciencenews.com/quantum-process-consciousness-27624/ As my expertise in neuroscience doesn't reach up to an ant's ear...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA
I am reading WHAT IS A QUANTUM FIELD THEORY?" A First Introduction for Mathematicians. The author states (2.4 Finite versus Continuous Models) that the use of continuity causes the infinities in QFT: 'Mathematicians are trained to think of physical space as R3. But our continuous model of physical space as R3 is of course an idealization, both at the scale of the very large and at the scale of the very small. This idealization has proved to be very powerful, but in the case of Quantum...
Back
Top