读博士期间，和教材一起合作炮制过一个利用自旋依赖光晶格中bloch振荡制备薛定谔猫的文章。这个文章先后被prl，epl，cpb拒稿。有趣的是，虽然都是负面意见，但是每一个审稿人意见又都不一样，重合很少。这让我们产生了一个新的想法，即把文章依次送到所有可能的物理杂志，收集一堆审稿意见，然后以此为案例写个心理学方面的文章。可惜教材着急毕业，不想玩了。文章最后在中国科学发表。

https://arxiv.org/abs/1107.0609  

这里公开过去的审稿意见

中文都是教材写的。没想到他保存得这么好，还认真总结，看得我想笑。

人生到处知何似，应似飞鸿踏雪泥。

泥上偶然留指爪，鸿飞那复计东西。

被拒稿多了，就成老油条了。

师兄廖蕾有个名言，写出来的文章一定有地方发表，所以被拒就转投呗。

======================================================

一、PRL的意见：

这两个意见中一个说没看懂我们文章中哪个和哪个纠缠，另一个说我们构建的不是薛定谔猫态——对于后者这个质疑，1996年的一篇Science中就已经使用了和我们一样的定义，并成为薛定谔猫的经典实验（这篇Science的文章我帖在邮件附件里，以供参考）。

Re: *****

   Wave packets macroscopically displaced with respect to each other via Bloch oscillation in a spin-dependent optical lattice

   by B. J. Wu and J. M. Zhang

Dear Dr. Zhang,

The above manuscript has been reviewed by our referees.

On the basis of the resulting reports, it is our judgment that the paper is unsuitable for publication in Physical Review Letters. We append comments from the criticism that led to our decision.

Yours sincerely,

Brant M. Johnson

Associate Editor

Physical Review Letters

The premier APS journal for current research

Email: prl@ridge.aps.org

Fax: 631-591-4141

http://prl.aps.org/

----------------------------------------------------------------------

Report of Referee A -- LH13551/Wu

----------------------------------------------------------------------

In this manuscript the Authors propose to use a spin dependent optical lattice, combined with a Bose-Einstein condensate (BEC) prepared in a superposition of two different hyperfine states, to create macroscopically separate wave packets each in one atomic hyperfine state. This is achieved by creating a BEC Bloch oscillator where the amplitude of the oscillation depends on the hyperfine state.

The Authors propose to use the presented method to create macroscopically entangled states. It is absolutely unclear to me what is entangled with what. The theoretical and experimental scheme proposed by the Authors looks exactly like a different realization of the Stern-Gerlach experiment, where no entanglement occurs. The atoms are prepared in a superposition of two quantum states, as the silver atoms in the original SG experiment were, and the role of the inhomogeneous magnetic field is here played by the optical lattice.

The optical lattice "measures" the hyperfine spin state of the single atom and spatially separates the two populations. The wavefunction Psi defined just above eq. 5 can be written as a two component spinor and the resulting eq 5 is in some sense a modified version of the Pauli equation. Of course, no magnetic fields are here involved but, as in the Pauli equation, we have a different potential for each spinor component.

To conclude, it seems to me that the proposal is, at best, a modern version of the Stern-Gerlach experiment with very limited interest. My second remark is that the paper is not clear on what is its strong claim. If the main result is the separation of two wave packets according to their spin, then as I said, this is nothing more than a "fancy" SG experiment. If the main claim is the preparation of an entangled state then I have strong doubts about this claim being correct. For these reasons I cannot recommend the acceptance in Physical Review Letters.

The Authors are also performing an experiment based on this proposal. My feeling is that they will reproduce the SG results. In this respect a realization of the full SG experiment using BEC and optical lattices might warrant a publication in the Physical Review A, where a more specialized audience could be addressed. Of course this will depend on a great deal on the quality and the outcome of the experiment.

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Report of Referee B -- LH13551/Wu

----------------------------------------------------------------------

I have read the manuscript LH13551 Wu. The authors claim to describe a scheme for the preparation of Schroedinger cat states. For that purpose they study Bloch oscillations in an optical lattice potential that depend on the internal state of an atom. I do not recommend publications in the Physical Review Letters, because the state the authors propose to create is not a Schroedinger cat state.

In detail:

The authors describe a single particle problem. They consider a single atom that is brought into a coherent superposition of two internal states. Via Bloch oscillations in a state sensitive optical lattice potential, this state evolves into a state that is a coherent superposition also of two spatially separated modes of the center of mass position of the atom. Such a state is not a Schroedinger cat. A Schroedinger cat state is a coherent superposition of a macroscopic number of degrees of freedom that collapses already when measuring a few degrees of freedom.

Even if the state the authors prepare would be realized with a Bose condensate of many particles, as the authors propose at the end of the manuscript, it would not correspond to a Schroedinger cat state. It would stay a single Bose condensate and a measurement of single particles either in the one or the other spatial mode would not cause a collapse, but leave the state of the remaining particles unchanged. And, even if it was an interesting goal to prepare the state the authors describe, using state-sensitive lattice potentials one can think of schemes that are much simpler and more robust as the one the authors propose. For example, in the deep lattice limit, one can simply move the lattice potentials felt by the two internal states in opposite directions.

二、EPL的审稿意见：

这两位审稿人并没有对机理提出质疑，但一位说观点并不新，类似的想法在10年前就有人提出过，而另一位审稿人说我们的工作是原创的，但是他觉得在实验上很难实现。

REF.: *****

Title:Schršdinger cat states prepared by Bloch oscillation in a spin-dependent optical lattice

Author(s):B.J. Wu and J.M. Zhang

Dear Mr. Wu,

The manuscript you submitted to EPL has been reviewed by two expert referees. I regret to inform you that on the basis of the attached resulting reports, we cannot accept your manuscript for publication.

Thank you for your understanding.

Yours sincerely,

on behalf of Professor Gora Shlyapnikov

Mr Frederic Burr

Staff Editor

REPORT A

In this paper the authors consider a condensate loaded in a spin dependent optical lattice. At some point, part of the atoms is transferred in a different hyperfine state and a linear force is applied.  Then, the two components start to perform Bloch oscillations with different amplitudes, producing a quantum state where internal and external degrees of freedom of the atoms are entangled (the hyperfine state and the center-of-mass, respectively). The authors suggest this procedure as a way to prepare a Schrodinger cat.

Though the idea is interesting, it is not new. In fact, the entanglement of the external and internal degrees of freedom of a condensate - obtained by exploiting the different external potential felt by the atoms in two different hyperfine states - was already considered about ten years ago, see e.g. the experiments performed at LENS (Minardi et al., PRL 87, 170401 (2001); Fort et al., Opt. Lett. 39, 1039 (2001)). Here the authors consider a different method (Bloch oscillations in a periodic potential instead of harmonic oscillations in a parabolic trap), but there is nothing conceptually new. Moreover, they only discuss the preparation of the system, but do not investigate possible physical implications and/or applications (they only mention about it).

Therefore, I think that this is not enough to justify a publication. Minor point: the introduction contains a lengthy initial part about Bloch oscillations. This is textbook stuff, that could be useful somewhere else to fix the notation, but it is certainly not suited for beginning the introduction.

REPORT B

The manuscript entitled "Schroedinger cat states prepared by Bloch oscillation in a spin-dependent optical lattice" by B.J. Wu and J.M. Zhang, reports on a mechanism to generate Schroedinger cat states with ultracold atoms where the internal degree of freedom such as the hyperfine state of an alkali atom is coupled to the center of mass position of the atomic wavepacket. Taking advantage of the varying polarizability of the atom upon the internal state, the atoms placed in an optical lattice and plus a linear potential follow periodic Bloch oscillations with amplitude strongly dependent on the internal state, resulting in the coupling of internal and external degrees of freedom and hence the claim of generating Schroedinger cat states.

The manuscript is clearly written and, to the best of my knowledge, the proposal is original.

Besides few statements that would require a clarification (see remarks below), I have a strong concern in recommending the publication of this proposal because in my opinion it would be extremely difficult to apply.

While the mechanism for entangling the internal and external degrees of freedom is clear, the authors miss a suitable discussion on the coherence properties of the state throughout the atomic trajectories.

The relative phase of the up and down states evolves summing up many contributions such as the different lattice potential depth seen by the atom depending on the internal state, the different trajectories in the external linear field, the radial dependence of the band structure of the lattice potential. These effects sum up quickly and on a time scale of the order of 50 ms, as suggested in the manuscript, I expect that the fluctuations tipical of experimental realizations, for instance on the lattice potential laser, would completely wash out the coherence between the two channels transforming the cat state into a statistical mixture

Without a thorough treatment of those technical decoherence processes I do not think that this manuscript would be of relevance for the scientific community it is aiming to. For this reason I do not recommend its publication on the European Physics Letters.

Remarks:

a) when the authors write

"...Subsequently, theta is adjusted to pi/2 (suddenly or smoothly, it does not matter; but in our simulation we take the sudden scenario),.."

and few paragraphs later

"..The reason is that due to the sudden change of theta, both wave packets are partially excited and some packets (not visible in the snapshots) belonging to higher bands are emitted around t = 0,..."

which is in contraddiction with the previous statement.

b) almost at the end of the paragraph, where the authors discuss a possible implementation of their scheme, they write:

"....For 87Rb and a lattice constant a = 392.5 nm, the ratio above corresponds to a tilt angle phi = 4 degrees and a period T = 53 ms....."

I guess that the direction is defined either from gravity or from the horizontal plane. The authors should define phi.

三、CPB的审稿意见：

这个审稿意见的主要观点可以归结为初始在|1>态下的BEC在打上脉冲之后，将会变成一部分在|1>态下，另一部分在|0>态下，整个BEC是这两部分的混合态，每一部分都对应各自的空间自由度，这不是一种叠加态，也不是纠缠态，所以谈不上薛定谔猫。

但事实上，初始在|1>态下的BEC在打上脉冲的时刻，的确是处在一个叠加态上，而不是自动成为一个混合态。因为在打上脉冲之后这团BEC中具体哪个原子会处在哪个态上，我们是不知道的，我们必须对这团BEC进行一次测量，才能明确知道哪些原子，或者说这个BEC的哪一部分是在|0>态，哪一部分在|1态>，然而这个测量恰恰会破坏原本的叠加态。这个审稿人认为初始在|1>态下的BEC在打上脉冲之后，将会变成一部分在|1>态下，另一部分在|0>态下，整个BEC是这两部分的混合态，这是在测量了这团BEC，破坏了原本的纠缠态之后才能得出的结论。

为了证明我们的观点是正确的，我在邮件附件中附上一篇2003年的PRL的实验文章，文章中刚巧支持了我们的观点。

In the manuscript the authors propose to create a Schrodinger cat state of ultracold atomic gases using a spin-dependent optical lattice and the Bloch oscillation. This topic is of current experimental and theoretical interests in cold atomic physics, however, the results derived in this work is physically incorrect. In fact, the authors misunderstood the concept of the cat state.

In general, the Schrodinger cat state of a macroscopic system often refers to a state with wave function similar to a|00...0>+b|11...1>, where |0> and |1> are two states that particles in the system reside in. However, the state, Eq. (6), proposed in the manuscript is obviously not of this form. Instead, equation (6) only states that atoms with spin |0> reside in state Psi_0 and those with spin |1> reside in state Psi_1. This type of wave function is not uncommon in ultracold atomic gases. For instance, in a spinor condensate, different spin components may have different spatial wave functions, which is clearly not a cat state.

For this reason, I do not recommend the publication of this manuscript.

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