Questions tagged [reversible-computing]
19 questions
10
votes
1 answer
A programming language that can only implement computable bijective functions?
Are there programming languages(or logic) that can implement(or express) a function $f:\mathbb{N}\to \mathbb{N}$ if and only if $f$ is a computable bijective functions?
Chao Xu
- 3,103
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10
votes
1 answer
What's flawed about the "save-the-input" method of reversible computing?
I'm an undergraduate just beginning to read about reversible computing. I know that, because of Landauer's principle, irreversible computations dissipate heat (and reversible ones do not). I brought it up with my professor, who had never heard of…
Eli Rose
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6
votes
1 answer
How Janus (Reversible Programming Language) `if`, `while`, and Update Work
In Reversible Computing, all program statements are reversible. I understand for example that the following:
\begin{align}
x\ {+}&{=}\ 4\\
y\ {*}&{=}\ x\\
x\ {-}&{=}\ 10
\end{align}
Has the inverse:
\begin{align}
x\ {+}&{=}\ 10\\
y\ {/}&{=}\ x\\
x\…
Lance Pollard
- 2,323
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4
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How to model reversible interactive programs
Reversible programs with finite execution steps are well studied. For example, a Turing machine whose transitions are reversible and halts can be executed backwards consuming its tape in the reverse order. A variant of Turing machines with distinct…
Akuri
- 41
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3
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1 answer
How to prove Landauer's principle
I have some questions about energy emitted when one bit of information is processed.
Landauer's principle states the minimum possible amount of energy required to erase one bit of information is k T ln2
Considering this,
How this formula is found?…
Onur A.
- 131
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3
votes
2 answers
Is it possible to make N-way Controlled-NOTs out of Toffoli gates, without extra work bits?
I'm working on exercise 4.29 of Nielsen and Chuang:
Find a circuit containing O(n^2) Toffoli, CNOT, and single qubit gates which implements a $C^n(X)$ gate (for n >3), using no work qubits.
As part of solving this exercise, I'm trying to figure…
Craig Gidney
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3
votes
1 answer
What difference does it make when universal classical gates in quantum computation are reversible but not unitary?
As I've come across Grovers algorithm I dont understand why when computing F(X), which is an oracle function people use classical reversible circuits(toffoli, fredkin) to evaluate the circuit. Why can't it just be done using classical logic…
CSK
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3
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1 answer
How to Implement a reversible OR operator with a Fredkin gate (controlled swap)?
How to implement a reversible OR operator with a Fredkin gate ?
Lokesh Pathak
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2
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1 answer
What is the relation between reversible circuits and invertible functions?
A reversible circuit, if I understand it correctly, is a circuit where every gate in the circuit is invertible, i.e. can simply be “turned in the opposite direction”, so that the entire circuit can in a sense just be “turned in reverse” without…
user56834
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Reversible computation and no cloning theorem in quantum computing
I am having a problem in understanding a conflict between reversibility in quantum computation and the No cloning theorem. Given a function f, we construct the reversible version of f by adding additional input and output wires to the circuit for f,…
acevik
- 73
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2
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1 answer
Would all objects in a reversible computing language be mutable?
Full disclosure, I'm asking this after watching a couple pop science videos; I do not know anything about the actual physics and hardware. I suspect the presenters expected an audience like me because they explained irreversibility at the level of a…
BatWannaBe
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2
votes
1 answer
Is this statistical group summation unambiguously reversible?
Let $X$ be a finite multisubset of $\mathbb{N}^2$. Let's introduce the following notation:
$A$ is a set of all first elements of pairs from $X$ and $B$ is a set of all second elements of pairs from $X$.
$cnt_1(n) = |\{(n, b)|(n, b) \in X\}|$ (that…
Tobias Hermann
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1
vote
0 answers
How to validate Bennett's reversible computation?
A reversible Turing machine ($\mathsf{RTM}$) is a Turing machine ($\mathsf{TM}$) whose transition function is a bijection, so that each instantaneous description ($\mathtt{ID}$) has at most one predecessor.
In [Ben73], Bennett showed that "Each…
Somudro Gupto
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1
vote
1 answer
Can you unwind a cryptographic hash function's last round?
Given a cryptographic hash, $ \text{hash}(A || B || C) $, and the last block added to the hash, $ C $, can you determine $ \text{hash}(A || B) $?
In other words, can you roll back the last round of a hash function, given that you know the input to…
Zaz
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1
vote
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Why isn't energy wasted with reversible computing? Isn't information discarded when we feed the function with a new input?
I understand that irreversible computing consumes energy because it has to "get rid" of outputs which have been used. With reversible computing that information is not "wasted" because with the outputs we can calculate the inputs again. But what…
Nicu Righeriu
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