REVIEW
Controlled Stark shifts in Er$^{3+}$-doped crystalline and amorphous waveguides for quantum state storage
Quantum Physics · Submitted 22 Mar 2006 · 24 references
Pith's verdict: First Stark coefficients in Er:LiNbO3 waveguides are a solid, direct result; the fiber number is model-dependent and the abstract should say so, but the paper deserves a serious referee.
T0 · AI review
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Referee report
The paper
The paper claims
Measured Stark coefficients of 25 ± 1 and 15 ± 1 kHz/Vcm^-1 in two erbium-doped waveguides confirm the waveguides can support quantum-state storage through controlled reversible inhomogeneous broadening.
The reading
What carries the argument
The central object is the linear DC Stark shift formula $\Delta\omega = (\Delta\mu_e \chi E / \hbar)\cos\theta$, where $\Delta\mu_e$ is the difference in permanent dipole moments between the two states, $\chi = (\epsilon + 2)/3$ is the Lorentz local-field correction, and $\theta$ is the angle between the dipole-moment difference and the applied field. Spectral hole burning isolates a narrow ensemble of ions so that the field-induced frequency change can be read directly. In the crystal, the LiNbO3 lattice fixes a single dipole direction, so the hole shifts; in the fiber, random orientations and a Maxwell distribution of dipole-difference magnitudes lead to the hole-shape function fitted to the data, from which the effective coefficient is extracted.
Extended reading notes
Core claim
The discovery is that both a crystalline and an amorphous erbium-doped waveguide exhibit a usable, reversible linear Stark effect on the $^{4}I_{15/2} \to {}^{4}I_{13/2}$ transition. In the LiNbO3 waveguide, an applied field along the C3 axis shifts the spectral hole as a whole; the slope of shift versus field gives $(\Delta\mu_e\chi)/h = 25 \pm 1\ \mathrm{kHz/V\,cm^{-1}}$, and the hole returns to its original position when the field is off. In the silicate fiber, where dipole orientations are random, the applied field broadens the hole according to the Maxwell-distribution and hole-shape model of Ref. [20]; fitting that model yields $(\Delta\mu_e\chi)/h = 15 \pm 1\ \mathrm{kHz/V\,cm^{-1}}$, and the hole width returns to its zero-field value when the field is removed. The paper concludes that these coefficients are sufficient to generate the roughly 100 MHz bandwidth needed for storing 10 ns pulses: a position-dependent field of about $\pm 2\ \mathrm{kV/cm}$ across the crystal, or a homogeneous field of about $3.5\ \mathrm{kV/cm}$ in the fiber, would produce the required controlled reversible inhomogeneous broadening.
Load-bearing premise
The fiber value stands on the assumption that the erbium ions' dipole-moment differences are randomly oriented and follow the Maxwell magnitude distribution used to fit the hole shapes; if that distributional model is wrong for this particular silicate glass, the quoted $15 \pm 1\ \mathrm{kHz/V\,cm^{-1}}$ would be systematically biased.
Editorial extensions
If this is right
- A CRIB quantum memory using a 6 mm LiNbO3 waveguide would require an applied field profile of roughly ±2 kV/cm across the crystal to encode the ~100 MHz bandwidth of 10 ns optical pulses.
- In the silicate fiber, a homogeneous field of about 3.5 kV/cm would produce the same controlled broadening, and the measured reversibility shows the broadening can be undone.
- Because the relevant erbium transition sits at 1.5 μm, a working memory of this type could connect directly to standard telecom fiber without wavelength conversion.
- The measured coefficients imply field strengths of a few kV/cm are sufficient, which is within the range achievable in compact electrode geometries.
Reading between the lines
- If the Maxwell-distribution model holds in this fiber, the same hole-shape fitting procedure should transfer to other rare-earth-doped amorphous waveguides, making it a general probe of Stark coefficients in glasses.
- The crystal's single dipole direction, a consequence of the non-centrosymmetric LiNbO3 structure, means a CRIB memory in this material can use a pure line shift rather than the pseudo-Stark splitting seen in centrosymmetric hosts, simplifying the required field geometry.
- One could test the model dependence of the fiber coefficient by measuring the hole broadening at much higher fields or at different angles between the field and the fiber axis; a systematic shape deviation would indicate a different dipole-moment distribution and a possibly corrected coefficient.
Original abstract
We present measurements of the linear Stark effect on the $^{4}$I$_{15/2} \to$ $^{4}$I$_{13/2}$ transition in an Er$^{3+}$-doped proton-exchanged LiNbO$_{3}$ crystalline waveguide and an Er$^{3+}$-doped silicate fiber. The measurements were made using spectral hole burning techniques at temperatures below 4 K. We measured an effective Stark coefficient $(\Delta\mu_{e}\chi)/(h)=25\pm1$kHz/Vcm$^{-1}$ in the crystalline waveguide and $(\bar{\Delta\mu_{e}}\chi)/(h)=15\pm1$kHz/Vcm$^{-1}$ in the silicate fiber. These results confirm the potential of Erbium doped waveguides for quantum state storage based on controlled reversible inhomogeneous broadening.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We present measurements of the linear Stark effect on the $^{4}$I$_{15/2} \to$ $^{4}$I$_{13/2}$ transition in an Er$^{3+}$-doped proton-exchanged LiNbO$_{3}$ crystalline waveguide and an Er$^{3+}$-doped silicate fiber. The measurements were made using spectral hole burning techniques at temperatures below 4 K. We measured an effective Stark coefficient $(\Delta\mu_{e}\chi)/(h)=25\pm1$kHz/Vcm$^{-1}$ in the crystalline waveguide and $(\bar{\Delta\mu_{e}}\chi)/(h)=15\pm1$kHz/Vcm$^{-1}$ in the silicate fiber. These results confirm the potential of Erbium doped waveguides for quantum state storage based on controlled reversible inhomogeneous broadening.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We present measurements of the linear Stark effect on the $^{4}$I$_{15/2} \to$ $^{4}$I$_{13/2}$ transition in an Er$^{3+}$-doped proton-exchanged LiNbO$_{3}$ crystalline waveguide and an Er$^{3+}$-doped silicate fiber. | contribution 1.00 | 0.93 | 0.04 | asserted 0.99 |
| s1 | The measurements were made using spectral hole burning techniques at temperatures below 4 K. | method 1.00 | 0.94 | 0.02 | asserted 1.00 |
| s2 | We measured an effective Stark coefficient $(\Delta\mu_{e}\chi)/(h)=25\pm1$kHz/Vcm$^{-1}$ in the crystalline waveguide and $(\bar{\Delta\mu_{e}}\chi)/(h)=15\pm1$kHz/Vcm$^{-1}$ in the silicate fiber. | result 1.00 | 0.97 | 0.09 | asserted 1.00 |
| s3 | These results confirm the potential of Erbium doped waveguides for quantum state storage based on controlled reversible inhomogeneous broadening. | interpretation 1.00 | 0.51 | 0.94 | asserted 0.67 |
What was examined, and what was not
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Figures
Figures reproduced from arXiv:quant-ph/0603194 by the authors.
References
Discussion
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