Turing machine and quantum computers

In summary, it is not possible to determine if a process in nature is computing a function that is not computable by a Turing machine based on observations alone. The only indication would be if the system cannot be described by a simple equation. However, since any function can be reproduced by a Turing machine, it is impossible to definitively determine if a black box is running an uncomputable system or a highly advanced Turing machine.
  • #1
bifolco84
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Can anyone help me...from Nielsen-Chuang "quantum computation and quantum information":how might we recognize that a process in nature computes a function not computable by a turing machine?
 
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  • #2
how might we recognize that a process in nature computes a function not computable by a turing machine
This can not be proven by observations alone. The strong hint would be that the system could not be described by any simple equation.

For any function (computable or not) there exists a Turing machine that can reproduce an arbitrary large finite subset of it. So if you have a black box producing some output, then you never know whether there is an uncomputable system inside or just a very smart Turing machine.
 

1. What is a Turing machine?

A Turing machine is a hypothetical computing device that was first proposed by Alan Turing in 1936. It consists of a tape divided into squares, a read/write head that can move left or right on the tape, and a set of rules that determine the machine's actions based on the current state and symbol on the tape. It is considered the foundation of modern computing and has been used to prove the limits of what can be computed.

2. How does a Turing machine differ from a classical computer?

A classical computer operates on a binary system, using 0s and 1s to represent data and instructions. A Turing machine, on the other hand, operates on an infinite tape divided into squares, with each square representing a symbol. This allows it to handle an infinite amount of data and perform any possible computation, although it may take a long time to do so.

3. What is the significance of a Turing machine?

A Turing machine is significant because it provides a theoretical framework for understanding the limits of computation. It showed that there are problems that cannot be solved by any algorithm, regardless of the computing power available. This concept is known as the "halting problem" and has important implications for computer science and artificial intelligence.

4. What are quantum computers and how do they differ from classical computers?

Quantum computers are a type of computing device that uses the principles of quantum mechanics to perform calculations. Unlike classical computers, which use bits to represent data, quantum computers use quantum bits, or qubits, which can exist in multiple states simultaneously. This allows quantum computers to solve certain problems much faster than classical computers, but they are still in the early stages of development and are not yet widely available.

5. Can a Turing machine be used to simulate a quantum computer?

Yes, a Turing machine can be used to simulate a quantum computer, but it would require an infinite amount of time and space. This is because quantum computers can handle an infinite amount of data, while a Turing machine has finite resources. Additionally, quantum computers use principles of quantum mechanics that cannot be accurately simulated by a classical computer, making it impractical to use a Turing machine for this purpose.

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