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UID:6abb09b889c66
DTSTART:20250328T100000Z
SEQUENCE:0
TRANSP:OPAQUE
DTEND:20250328T110000Z
LOCATION:Seminar Room
SUMMARY:ICFO | GRZEGORZ RAJCHEL-MIELDZIOĆ
CLASS:PUBLIC
DESCRIPTION:The ability to characterise and discern quantum&nbsp\;channels&
 nbsp\;is a crucial aspect of noisy quantum technologies.&nbsp\; In this wo
 rk\, we explore the problem of distinguishing quantum&nbsp\;channels&nbsp\
 ;when limited to&nbsp\;sub-exponential resources\, framed as von Neumann (
 projective) measurements. We completely characterise equivalence classes o
 f quantum&nbsp\;channels&nbsp\;with different Kraus ranks that have the sa
 me marginal distributions&nbsp\;under&nbsp\;compatible projective measurem
 ents. In doing so\, we explicitly identify gauge freedoms which can be var
 ied without changing those compatible marginal outcome distributions\, ope
 ning new avenues for quantum channel simulation\, variational quantum chan
 nels\, as well as novel adversarial strategies in noisy quantum device cer
 tification. Specifically\, we show how a Sinkhorn-like algorithm enables u
 s to find the minimum admissible Kraus rank that generates the correct out
 come marginals. For a generic d-dimensional quantum system\, this lowers t
 he Kraus rank from d^2 to the theoretical minimum of d. For up to d = 20\,
  we numerically demonstrate our findings\, for which the code is available
  and open source.&nbsp\; Finally\, we provide an analytic algorithm for th
 e special case of&nbsp\;spoofing&nbsp\;Pauli&nbsp\;channels.\n&nbsp\;
DTSTAMP:20260929T004336Z
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