We comment on an analysis by Qureshi of an experiment proposed by Popper and show that an analysis based solely on conventional nonrelativistic quantum mechanics is sufficient to exclude the possibility of subluminal or superluminal communication. That is, local operations cannot be employed to transmit information.

1.
Tabish
Qureshi
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Understanding Popper’s experiment
,”
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73
,
541
544
(
2005
).
2.
K. R.
Popper
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(
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,
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,
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), pp.
27
29
.
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K. R.
Popper
, “
Realism in quantum mechanics and a new version of the EPR experiment
,” in
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G.
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and
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4.
Asher
Peres
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Classical interventions in quantum systems. II: Relativistic invariance
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5.
Asher
Peres
, “
How the no-cloning theorem got its name
,” quant-ph/0205076.
6.
Tabish
Qureshi
, private communication, June 16,
2005
.
7.
Tabish
Qureshi
, “
Popper’s experiment. Copenhagen interpretation and nonlocality
,” quant-ph/0301123.
8.
D.
Bruss
,
G. M.
DAriano
,
C.
Macchiavello
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M. F.
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Approximate quantum cloning and the impossibility of superluminal information transfer
,”
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Asher Peres, “
Opposite momenta lead to opposite directions
,”
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N. D.
Mermin
, “
From cbits to qubits: Teaching computer scientists quantum mechanics
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30
(
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especially the discussion in Sec. VI of the Born rule. See also the corresponding discussion in
E.
Gerjuoy
, “
Shor’s factoring algorithm and modern cryptography. An illustration of the capabilities inherent in quantum computers
,”
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11.
K.
Gottfried
,
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(
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,
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,
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), pp.
235
240
.
12.
See, for example,
W.
Heitler
,
The Quantum Theory of Radiation
(
Clarendon Press
, Oxford,
1954
), pp.
38
ff.
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