Recording density limit of photon-echo optical storage with high-speed writing and reading

Abstract

The first analysis to our knowledge of the optical data storage density of photon-echo storage is presented. Mainly considering signal-to-noise ratio performance, we calculate the obtainable storage density for data storage and processing using photon echoes to be approximately 100 times the theoretical limit for conventional optical data storage. This limit is similar to that theoretically calculated for data storage by use of persistent spectral hole burning. For storage times longer than the upper-state lifetime the highest densities can, however, be obtained only if all the excited atoms decay, or are transferred, to a different state than that from which they were originally excited. The analysis is restricted to samples with low optical density, and it also assumes that for every data sequence, writing is performed only once. It is therefore not directly applicable to accumulated photon echoes. A significant feature of photon-echo storage and processing is its speed; e.g., addressing 1 kbyte/(spatial point) permits terahertz read and write speeds for transitions with transition probabilities as low as 1000 s 1 .

Quantum processing with ensembles of rare-earth ions in a stoichiometric crystal

“…If the ensemble qubit system were used for quantum computing rather than photonic state processing, larger numbers of qubits are possible since the optical depth can be low and the ensemble small. Detection of ensembles containing O(10 4 ) ions with good signal-to-noise ratios is possible with fairly conventional optical setups [57], which means five to seven qubit systems could be created in existing materials. To see this, consider a crystal with a 250 Å3 volume per rare earth atom (e.g.…”

Influence of laser phase and frequency fluctuations on photon-echo data erasure

“…An additional complication that has not been discussed occurs if the efficiency in the writing process is large, i.e., the branching ratio ␤ for the upper-state relaxation to the reservoir state is large, which is desirable for photon-echo storage; see, e.g., Ref. 7. If ␤ is large and if the data rate is sufficiently high there will be a buildup of the population in the reservoir state.…”

“…6) and bit rates of ϾTbits/s (Ref. 7) have been projected and achieved 8 for these types of memory. Frequency-selective optical memories are based on materials with inhomogeneously broadened absorption lines and, in particular, on the property that it is possible selectively to address a large number of different frequency packets within such an absorption line in these materials.…”

Experimental demonstration of data erasure for time-domain optical memories

“…There is the potential for enormous storage densities with data accessible at very high speeds, and these capabilities make the coherent time-domain optical memories attractive for the next generation of optical memories. 6,7 An additional capability of the time-domain technique, which is essential if the memories are to have widespread usage, is the ability to modify the stored data. The additional process required for this is the ability to erase single data bits once stored.…”