| Issue |
Europhys. Lett.
Volume 75, Number 2, July 2006
|
|
|---|---|---|
| Page(s) | 195 - 201 | |
| Section | General | |
| DOI | https://doi.org/10.1209/epl/i2006-10105-x | |
| Published online | 16 June 2006 | |
Superbroadcasting of conjugate quantum variables
1
Dipartimento di Fisica “A. Volta” and CNISM - via Bassi 6, I-27100 Pavia, Italy
2
CNR - Istituto Nazionale per la Fisica della Materia, Unità di Pavia - Italy
Received:
7
April
2006
Accepted:
29
May
2006
We consider the problem of broadcasting arbitrary states of
radiation modes from N to 
copies by a map that preserves
the average value of the field and optimally reduces the total noise
in conjugate variables. For 
the broadcasting can be
achieved perfectly, and for sufficiently noisy input states one can
even purify the state while broadcasting—the so-called superbroadcasting. For purification (i.e. 
), the reduction of noise is independent of M. Similar results are
proved for broadcasting with phase-conjugation. All the optimal maps
can be implemented by linear optics and linear amplification.
PACS: 03.65.-w – Quantum mechanics / 03.67.-a – Quantum information
© EDP Sciences, 2006
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