On the Relation Between Quantum Computational Speedup and Retrocausality

  title={On the Relation Between Quantum Computational Speedup and Retrocausality},
  author={Giuseppe Castagnoli},
We investigate the reason for the quantum speedup (quantum algorithms require fewer computation steps than their classical counterparts). We extend the representation of the quantum algorithm to the process of setting the problem, namely choosing the function computed by the black box. The initial measurement selects a setting at random, Bob (the problem setter) unitarily changes it into the desired one. With reference to the observer dependent quantum states of relational quantum mechanics… 

Completing the physical representation of quantum algorithms explains their computational speedup

An optimal quantum algorithm is a sum over classical histories in each of which Alice knows in advance one of the possible halves of the solution and performs the computation steps necessary to identify the missing half.

Completing the physical representation of quantum algorithms provides a retrocausal explanation of their speedup

A fundamental justification for the explanation of the speedup is provided and it is shown that it answers the well accepted requirement of the completeness of the physical description of quantum algorithms by just completing the physical representation ofquantum algorithms.

Completing the Physical Representation of Quantum Algorithms Provides a Quantitative Explanation of Their Computational Speedup

The physical representation of the usual representation of quantum algorithms shows that the number of computation steps required to solve any oracle problem in an optimal quantum way should be that of a classical algorithm endowed with the advanced knowledge of half solution.

3D Image Encryption Algorithm Based on Quantum Random Walk and Multidimensional Chaos

The blind watermark embedding algorithm based on DCT and SVD is used to embed the watermark information into the encrypted image, so that the receiver can extract theWatermark information and judge whether the image is damaged by attack in the process of transmission according to the integrity of the water Mark, which improves the protection of image information security.

Quantum Confidentiality Query Protocol Based on Bell State Identity



Contextuality supplies the ‘magic’ for quantum computation

This work proves a remarkable equivalence between the onset of contextuality and the possibility of universal quantum computation via ‘magic state’ distillation, which is the leading model for experimentally realizing a fault-tolerant quantum computer.

On the power of quantum computation

  • Daniel R. Simon
  • Computer Science
    Proceedings 35th Annual Symposium on Foundations of Computer Science
  • 1994
This work presents here a problem of distinguishing between two fairly natural classes of function, which can provably be solved exponentially faster in the quantum model than in the classical probabilistic one, when the function is given as an oracle drawn equiprobably from the uniform distribution on either class.

Disentangling the Quantum World

This work exploits some simple symmetries to show how Costa de Beauregard's zigzag needs to work, to explain the correlations at the core of Bell's Theorem.

M ay 2 00 6 Information-theoretic temporal Bell inequality and quantum computation

Separation between classical and quantum phenomena plays a crucial role in understanding the weirdness of quantum physics and has recently been extensively investigated, especially in the context of

Quantum correlation between the selection of the problem and that of the solution sheds light on the mechanism of the quantum speed-up

Both the quadratic and exponential speed-ups are explained by the fact that quantum algorithms start from this advanced knowledge, which gives to Alice advanced knowledge of 50% of the information that specifies the solution.

Relational quantum mechanics

I suggest that the common unease with taking quantum mechanics as a fundamental description of nature (the “measurement problem”) could derive from the use of an incorrect notion, as the unease with

On the role of entanglement in quantum-computational speed-up

  • R. JozsaN. Linden
  • Physics, Computer Science
    Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences
  • 2003
It is argued that it is nevertheless misleading to view entanglement as a key resource for quantum‐computational power, as it is necessary for any quantum algorithm to offer an exponential speed‐up over classical computation.

Quantum computing, postselection, and probabilistic polynomial-time

  • S. Aaronson
  • Computer Science
    Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
  • 2005
It is shown that several simple changes to the axioms of quantum mechanics would let us solve PP-complete problems efficiently, or probabilistic polynomial-time, and implies, as an easy corollary, a celebrated theorem of Beigel, Reingold and Spielman that PP is closed under intersection.

Most quantum States are too entangled to be useful as computational resources.

It is shown that quantum states can be too entangled to be useful for the purpose of computation, in that high values of the geometric measure of entanglement preclude states from offering a universal quantum computational speedup.

Quantum theory, the Church–Turing principle and the universal quantum computer

  • D. Deutsch
  • Physics, Philosophy
    Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences
  • 1985
It is argued that underlying the Church–Turing hypothesis there is an implicit physical assertion. Here, this assertion is presented explicitly as a physical principle: ‘every finitely realizible