Dear Dr. Troyer and users of ALPS,

I am trying to measure local magnetization with   

MEASURE_LOCAL[Local magnetization]=Sx

for the following model:

<HAMILTONIAN name="my spin model 1">

  <BASIS ref="spin"/>

  <SITETERM site="i">

     -2*xi*Sz(i)-2*h*Sx(i)

  </SITETERM> 

  <BONDTERM source="i" target="j">

     -g*(Splus(i)*Sminus(j)+Sminus(i)*Splus(j))

  </BONDTERM>

</HAMILTONIAN>

Value of parameter xi depends on the site in an actual problem, 

but this is not important now.

Since dirloop_sse says that "Offdiagonal site terms 

are not implemented in this SSE code", I use the worm code.

Worm code says the following for this:

"Will not measure "Local magnetization" since it is 

off-diagonal or not a site operator".

As a trick to overcome this problem,

I tried to rotate the coordinate system

in order to measure the required values with 

MEASURE_LOCAL[Local magnetization]=Sz

In this case the rotated model is:

<SITEOPERATOR name="Sy" site="x">

  1/2/I*(Splus(x)-Sminus(x))

</SITEOPERATOR>

<HAMILTONIAN name="my spin model 2">

  <BASIS ref="spin"/>

  <SITETERM site="i">

     -2*xi*Sy(i)-2*h*Sz(i)

  </SITETERM> 

  <BONDTERM source="i" target="j">

     -2*g*Sz(i)*Sz(j)-2*g*Sx(i)*Sx(j)

  </BONDTERM>

</HAMILTONIAN>

Now the worm code says the following:

"can not convert complex number into real one".

Therefore, the worm code does not seem to understand Sy(i) as

a site term in Hamiltonian (?).

Finally, I tried another version of rotation, which

also would allow to measure with

MEASURE_LOCAL[Local magnetization]=Sz

The rotated model is:

<SITEOPERATOR name="Sy" site="x">

  1/2/I*(Splus(x)-Sminus(x))

</SITEOPERATOR>

<HAMILTONIAN name="my spin model 3">

  <BASIS ref="spin"/>

  <SITETERM site="i">

     2*xi*Sx(i)-2*h*Sz(i)

  </SITETERM> 

  <BONDTERM source="i" target="j">

     -2*g*Sz(i)*Sz(j)-2*g*Sy(i)*Sy(j)

  </BONDTERM>

</HAMILTONIAN>

Now the worm code says the following:

"Cannot simulate this bond term with the worm code".

Therefore, the worm code does not seem to 

understand Sy(i)*Sy(j) as a bond term 

in Hamiltonian (?).

Could you let me know whether there are

ways to perform the measurement ?

Sincerely yours,

Lev Barash