Quantum computations without definite causal structure

By Giulio Chiribella, Giacomo Mauro D'Ariano, Paolo Perinotti, Benoît Valiron. 2009

560 citations recorded by the source corpus.

We show that quantum theory allows for transformations of black boxes that cannot be realized by inserting the input black boxes within a circuit in a pre-defined causal order. The simplest example of such a transformation is the classical switch of black boxes, where two input black boxes are arranged in two different orders conditionally on the value of a classical bit. The quantum version of this transformation-the quantum switch-produces an output circuit where the order of the connections is controlled by a quantum bit, which becomes entangled with the circuit structure. Simulating these transformations in a circuit with fixed causal structure requires either postselection, or an extra query to the input black boxes.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/bedac6e57e7a795f44ba1356324da4770e34ecaf

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In Artificial Intelligence

In Atomic and Molecular Physics, and Optics

Citations in the corpus

Experimental superposition of orders of quantum gates (2014, background): “another set of qubits – this is not allowed in the standard quantum circuit model, wherein the gate order is independent of the state of the qubits [2].”