Measuring a nonlocal observable on a space-like separated quantum system is a resource-hungry and experimentally challenging task. Several theoretical measurement schemes have already been proposed to increase its feasibility, using a shared maximally-entangled ancilla. We present a new approach to this problem, using the language of generalized quantum measurements, to show that it is actually possible to measure a nonlocal spin product observable without necessarily requiring a maximally-entangled ancilla. This approach opens the door to more economical arbitrary-strength nonlocal measurements, with applications ranging from nonlocal weak values to possible new tests of Bell inequalities. The relation between measurement strength and the amount of ancillary entanglement needed is made explicit, bringing a new perspective on the links that tie quantum nonlocality, entanglement and information transmission together.

在类似空间的分离量子系统上测量非局域可观测性是一项资源匮乏且具有实验挑战性的任务。已经提出了几种理论测量方案来提高其可行性，使用共享的最大纠缠附件。我们提出了一种解决这个问题的新方法，使用广义量子测量的语言，以表明实际上可以测量可观察到的非局域自旋积，而不必需要最大纠缠的辅助。这种方法为更经济的任意强度非局部测量打开了大门，其应用范围从非局部弱值到贝尔不等式的可能新测试。测量强度和所需的辅助纠缠量之间的关系是明确的，