# Questions tagged [reversible-computation]

For questions related to reversible computing, i.e. computing models where each elementary operation (and hence every computation) can be undone.

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### How universal is the Toffoli gate for classical reversible computing?

It is easy to see that no finite set of classical reversible gates can be strictly universal (without ancilla) for classical reversible computation: for any reversible gate on $n$ bits, in its action ...
165 views

### Thermodynamic Speed Limit to Quantum Computing

There's a lot of mystifying jargon in the field of quantum computation, so I would like to pose a question from elementary physics to maybe help clarify things. Is it not true that the speed of a real-...
110 views

### Universality for reversible classical computation

Is there any way to check whether a set of gates (for example, take the set comprising of the CNOT gate and the Hadamard gate) is universal for reversible classical computation? I can think of trial ...
184 views

### How does one convert a truth table to a square permutation matrix?

Given a classical circuit of $m$ inputs and $n$ outputs, composed of various AND gates, OR gates, NOT gates, etc., a truth table is a $2^{m}\times(m+n)$-sized matrix, where, in general, the first $m$ ...
119 views

### How to build a quantum circuit of a given reversible function?

Given a function $f : \{0,1\}^n \longrightarrow \{0,1\}^m$ and a function $g : \{0,1\}^m \longrightarrow \{0,1\}^n$ that both can be computed by polynomial-size classical circuits such that $g(f(x))=x$...
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### "Bennett’s trick" for reversible circuits

A textbook approach, attributed to Charlie Bennett, for creating reversible circuit which outputs the input qubits and the initialized ancilla qubits involves copying the function output between the ...
120 views

### What role does Landauer's principle play in quantum reversibility?

In section 3.2.5 of Nielsen and Chuang (starting page 153) they talk about Landauer’s principle, where they discuss the lower bound on the thermodynamic cost of erasing information. In irreversible ...
1 vote
I read unitary matrices are reversible, so when we apply a unitary operator $U$ on some input state and got an output state, then if we apply $U^\dagger$ (transpose conjugate) we get back the original ...
I have been reading about Bernstein-Vazirani Algorithm, and it uses what is known as a phase oracle. Basically, it is CNOT gate with several controls attached to the ancilla qubit $|-\rangle$ (it is ...