In a given non-real algebraic number field (say, given by an irreducible polynomial over $\mathbb{Q}$) is there a complexity bound on the summands $x,\dots,t$ that make $-1$ a sum of squares? So $x^2+\dots+t^2=-1$.


Can you show that if $-1$ is a sum of squares at all, then it is a sum of some list of summands subject to some bound? 


I would like to learn of an exponential bound. Say, an exponential function of the Weil heights of the rational coefficients of the defining polynomial, which serves as upper bound on the Weil heights of the rational coefficients of $x,\dots,t$ in the power base by the variable of the defining polynomial. 


Of course if some other representation is more useful for the problem that's great with me.


To be clear, I am not asking how many summands it takes (I chose $x\dots t$ to suggest the four $x,y,z,t$). I am asking how complex they need to be. The shortest sum might not have the simplest entries. 



Is realness of number fields exponentially bounded?
To answer the comment above; sure. There's a theorem of Cassels,
generalized to number fields by Raghavan "Bounds for minimal solutions of Diophantine equations," (MR0485681) which gives a concrete upper bound for the smallest solution to a quadratic form (when they exist). 


Namely, given an anisotropic quadratic form, there's a solution in the ring of integers with a bound that depends only on the discriminant of the number field, the size of the coefficients, and the number of variables. In this case, because the quadratic form is fixed, the bound depends only on the discriminant, explicitly;


$$|x\_i| \le 625 |\Delta\_F|^{5/2[F:\mathbb{Q}]}$$


