Quantum process tomography with coherent states

Saleh Rahimi-Keshari, Artur Scherer, Ady Mann, A. T. Rezakhani, A. I. Lvovsky, Barry C. Sanders

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)


We have developed an enhanced technique for characterizing quantum optical processes based on probing unknown quantum processes only with coherent states. Our method substantially improves the original proposal (Lobino et al 2008 Science 322 563), which uses a filtered Glauber-Sudarshan decomposition to determine the effect of the process on an arbitrary state. We introduce a new relation between the action of a general quantum process on coherent state inputs and its action on an arbitrary quantum state. This relation eliminates the need to invoke the Glauber-Sudarshan representation for states; hence, it dramatically simplifies the task of process identification and removes a potential source of error. The new relation also enables straightforward extensions of the method to multi-mode and non-trace-preserving processes. We illustrate our formalism with several examples, in which we derive analytic representations of several fundamental quantum optical processes in the Fock basis. In particular, we introduce photon-number cutoff as a reasonable physical resource limitation and address resource versus accuracy trade-off in practical applications. We show that the accuracy of process estimation scales inversely with the square root of photon-number cutoff.

Original languageEnglish
Article number013006
Pages (from-to)1-17
Number of pages17
JournalNew Journal of Physics
Publication statusPublished - 11 Jan 2011
Externally publishedYes


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