Not for QMC and long times, since the real time evolution gives complex phases in the weights.
Matthias
On 3 Aug 2011, at 11:16, Dan Thompson wrote:
> I think I understand what you mean now. It isn't possible to simulate a dynamic hamiltonian with alps. Ie., a MC time-dependent hamiltonian.
> -Dan
>
> On Wed, Aug 3, 2011 at 1:39 PM, Matthias Troyer <troyer(a)phys.ethz.ch> wrote:
> Hi Dan,
>
> That only makes sense if you are interested in the efficiency of our QMC algorithms. But the annealing time T in this scheme has nothing do to with real time.
>
> Matthias
>
> On 3 Aug 2011, at 10:37, Dan Thompson wrote:
>
>> Hey Matthias,
>>
>> Thanks for the quick reply. Here's what I'm trying to do with the alps qmc code:
>> - Initially, I want to start with a quantum spin 1/2 system in a strong, transverse magnetic field. It should be in the ground state of this particular hamiltonian.
>> - Then, the idea is to simulataneously:
>> a) turn off the transverse field
>> b) turn on a field along the spin axis and
>> c) turn on couplings between the various spins.
>> This would be the quantum annealing part and should take T MC time.
>> - After the annealing, I would measure the new state of the spin system. Namely, I would look at the fidelity of this state and the ground state of the hamiltonian with the couplings and field along the spin axis.
>>
>> Does that make more sense? The idea would be to measure how the fidelity changes as the annealing time T changes.
>>
>> Cheers,
>> -Dan
>>
>>
>>
>> On Wed, Aug 3, 2011 at 12:50 PM, Matthias Troyer <troyer(a)phys.ethz.ch> wrote:
>>
>> On 3 Aug 2011, at 09:40, Dan Thompson wrote:
>>
>> > Hello,
>> >
>> > I was just wondering if there was a way to simulate the quantum annealing of a spin chain/lattice. Namely, adjust the parameters in a model file so that over the course of the quantum monte carlo simulation I could start with one hamiltonian (a simple heisenberg hamiltonian with nearest neighbour couplings and a transverse magnetic field) and finish with a different one (transverse field turned off).
>> >
>> > Cheers,
>> > -Dan
>>
>> Hi Dan,
>>
>> What is the purpose of this? Do you want to use it to improve the simulation or to get some time-dependent measurements? The QMC codes only measure equilibrium properties at the given parameters and you can thus just do a series of simulations. Please remember that MC time and real time are not the same.
>>
>> Matthias
>>
>>
>
>