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Quantum Information Processing

Nonlocality without entanglement: an acyclic configuration

Atanu Bhunia, Indrani Chattopadhyay, Debasis Sarkar

Published Apr 30, 2022• 13 citations
Publisher
DOI
10.1007/s11128-022-03506-9

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This manuscript reframes a series of IBM superconducting-qubit experiments as a targeted validation study for the Directed Acyclic Graph Interpretation (DAGI), with emphasis on the operational distinction between \emph{record creation} and \emph{record erasure}, and on how that distinction manifests in different classes of observables. DAGI models quantum processes as a directed acyclic graph of informational events: branching is permitted only when an interaction produces a durable record at the relevant coarse-graining scale, while coherent erasure can restore interference by removing the distinguishing record. We consolidate three falsifier-friendly hypotheses: (H1) remote record activity need not produce a universal ``clock slowdown'' for arbitrary local probes; (H2) remote influence is expected to appear preferentially in observables supported by a relational/entangled substrate; and (H3) the record/eraser distinction should be directly visible in distributed witnesses under strictly pulse-matched controls. Using the C1 ``informational time dilation'' series as the local benchmark, and the T4 remote-closure suite as the nonlocal stress test, we report a split outcome: clock-side remote slowdown remains bounded and proxy-dominated in tested geometries, yet a GHZ-class distributed coherence witness exhibits a large, replicated record-creation (REC) versus reversible sham (SHAM) separation on both ibm_fez and ibm_marrakesh, and is strongly restored by coherent erasure (ERASE). We position this pattern as evidence for observable-selective remote sensitivity that is consistent with DAGI's record/eraser mechanism while remaining conservative about hardware backaction channels.

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The study of quantum nonlocal correlations in networks (QNCNs), beyond the standard Bell theory with a single source, involves simulating large-scale quantum communications. The detectability of QNCNs depends on the input sources and selected measurements, and more essentially on the network structures. In this paper, we prove that same-size acyclic networks with different independence degrees can generate distinct sets of QNCNs in the device-independent scenario. We then distinguish two acyclic networks with different independence degrees by comparing the QNCNs generated from them. Furthermore, we show quantum demonstrations of the aforementioned notions in two-qubit-source networks. We investigate the quantitative influence of different network topologies on the detection of QNCNs in acyclic networks with Werner states as sources. Finally, we study how to maintain high independence degrees in networks formed by connecting two networks. This makes the correlations on the newly formed quantum network more likely to be nonlocal. Our research provides an alternative perspective for the well-known graph classification problem, and establishes an intrinsic connection between the graph theory and the foundation of quantum mechanics.
We present a variational quantum eigensolver (VQE) algorithm for the efficient bootstrapping of the causal representation of multiloop Feynman diagrams in the loop-tree duality or, equivalently, the selection of acyclic configurations in directed graphs. A loop Hamiltonian based on the adjacency matrix describing a multiloop topology, and whose different energy levels correspond to the number of cycles, is minimized by VQE to identify the causal or acyclic configurations. The algorithm has been adapted to select multiple degenerated minima and thus achieves higher detection rates. A performance comparison with a Grover's based algorithm is discussed in detail. The VQE approach requires, in general, fewer qubits and shorter circuits for its implementation, albeit with lesser success rates.
This manuscript reframes a series of IBM superconducting-qubit experiments as a targeted validation study for the Directed Acyclic Graph Interpretation (DAGI), with emphasis on the operational distinction between \emph{record creation} and \emph{record erasure}, and on how that distinction manifests in different classes of observables. DAGI models quantum processes as a directed acyclic graph of informational events: branching is permitted only when an interaction produces a durable record at the relevant coarse-graining scale, while coherent erasure can restore interference by removing the distinguishing record. We consolidate three falsifier-friendly hypotheses: (H1) remote record activity need not produce a universal ``clock slowdown'' for arbitrary local probes; (H2) remote influence is expected to appear preferentially in observables supported by a relational/entangled substrate; and (H3) the record/eraser distinction should be directly visible in distributed witnesses under strictly pulse-matched controls. Using the C1 ``informational time dilation'' series as the local benchmark, and the T4 remote-closure suite as the nonlocal stress test, we report a split outcome: clock-side remote slowdown remains bounded and proxy-dominated in tested geometries, yet a GHZ-class distributed coherence witness exhibits a large, replicated record-creation (REC) versus reversible sham (SHAM) separation on both ibm_fez and ibm_marrakesh, and is strongly restored by coherent erasure (ERASE). We position this pattern as evidence for observable-selective remote sensitivity that is consistent with DAGI's record/eraser mechanism while remaining conservative about hardware backaction channels.