arXiv subjects

Eran Kopel

Publications and source records attributed to Eran Kopel.

3 recordsLinked to original sources

arXiv2026

Certified measurement and control of an entanglement-breaking index on programmable hardware

The entanglement-breaking index of a quantum channel, the number of self-compositions after which the channel destroys all entanglement with any reference, has to our knowledge never been measured. We show that a certified thermal collision feedback loop makes this integer both measurable and controllable on current programmable hardware, every load-bearing quantity delivered as an interval-arithmetic certificate. On the measurement side: a target list for the integer staircase n_EB(p) with decision-point negativities certified at margins 0.025 to 0.109; an exact per-round depolarising model in which the selected staircase survives realistic noise as certified integers; an exact, tight compilation of the round unitary (seven CNOTs all-to-all, five native arbitrary-angle gates, ten on heavy-hex); and a 33-million-draw gated search bounding the thermal valley's contrast by a wall with an interior maximum, a certified 2.85x10^-3 near floor 89. On the control side: the model composes rounds of differing bath polarisation exactly, so the valley becomes a pulsed valve, switching at a certified minimal pulse of exactly eight rounds; the optimal pulsed signal, a certified 3.43x10^-3, beats the static protocol, so the best valley measurement is intrinsically pulsed; and a coherent tilt of the bath Bloch vector lifts the signal to a certified 8.6x10^-3, three times the static ceiling, at zero population cost. Valley signatures certifiably die near per-round noise strength 10^-4, fixing the error-extrapolation burden. The staircase is a near-term experiment; the pulsed valley a precisely priced one.

quant-ph↗

arXiv2026

Certified coherent, informative, and non-entanglement-breaking fixed points of future-referential quantum feedback

We study quantum processes in which information extracted from a forward simulation is returned as input to an earlier internal time of the simulated dynamics: externally the protocol is an ordinary causally ordered circuit, but internally it is future-referential. Contracting a process tensor with a leakage instrument and a controller induces a completely positive trace-preserving map on a message register, and we classify its fixed points by five operational properties: stability, informativeness, feedability, coherence, and preservation of quantum correlations. Four results separate notions that informal discussions of "information from the future" often conflate. A two-parameter unitary-dilation family yields a closed-form, globally attractive, coherent fixed point (Proposition 1), yet is entanglement breaking whenever future records are perfectly distinguishable (Lemma 1). Releasing that orthogonality, a four-parameter partial-swap family admits a nonempty open non-entanglement-breaking region (Proposition 2), with an explicit Choi partial-transpose neighborhood of half-width $0.0163\pi$ (Proposition 3). Combining outward-rounded interval enclosures with perturbation bounds tracking the channel and its stationary-state drift, we certify an explicit parameter square of half-width $0.0013\pi$ on which the feedback channel is simultaneously strictly contractive (margin $\ge 0.237$), coherent ($\ge 0.416$), informative about the designated future variable ($\ge 0.172$ bits), and non-entanglement-breaking (NPT margin $\ge 0.188$) (Proposition 4). Direct evaluation shows all four properties persisting over a region an order of magnitude larger, so the certified square is a proof of principle rather than a phase boundary. All enclosures and margins are confirmed by a machine-verified ball-arithmetic certificate, and the complete code and certificate accompany the paper.

quant-ph↗

arXiv2026

How many labels can a biological oscillator carry? A quality-factor screen for proposed information carriers

How many distinguishable labels can a biological oscillator carry? Proposals invoking collective vibrational modes, endogenous electromagnetic fields, microtubule excitations and oscillatory phase codes are each debated on grounds particular to themselves, with no shared standard for comparison. We show that spectral distinguishability alone bounds the number of labels by the quality factor, M <= Q = 2 pi nu tau. This follows from the relation between linewidth and coherence time, so it is independent of substrate, of mechanism, and of any position on quantum effects in biology, and it can be evaluated from two published quantities. Applied to a recently proposed 30 GHz intracolumnar microwave field in cortex, it gives Q = 0.19: the linewidth exceeds the carrier five-fold. The obvious rescue, that a driven emitter can be spectrally narrower than its gain medium, requires a resonant cavity, and the model's own geometry forbids one. An independent bound on metabolic power is exceeded by five to nine orders of magnitude. Six further criteria follow from the same standpoint, including a two-sided persistence window requiring a label to be both readable and rewritable. Screening eleven carriers, only the low-frequency neural rhythms pass. High-frequency molecular carriers are eliminated by brevity, not by the fragility the debate has assumed.

q-bio.NC↗