A problem about qubit register release

[hofirstb]

Description:

In the following test case, there is a strange memory release problem when the non-all-zero qubits are not measured, and the error line information is ambiguous because there is nothing to do in line 13. At the same time, if the X operation replaces IncrementByModularInteger, the same phenomenon will occur. And MultiM operation does not reset the measured qubits to the |0⟩ state. So can you give me some suggestions about why this behavior occurred?

Testcase

namespace NISLNameSpace {
	open Microsoft.Quantum.Intrinsic;
	open Microsoft.Quantum.Measurement;
	open Microsoft.Quantum.Arithmetic;
		
	@EntryPoint()
	operation main() : Unit {
		mutable constMultiplier = 88;
		mutable modulus = 1024;
		use summand = Qubit[10];
		let summandLE = LittleEndian(summand);
		IncrementByModularInteger(constMultiplier, modulus, summandLE);
		// X(summand[0]);
		// mutable result = MultiM(summandLE!);
		// Message($"{result}");
	}
}

Environment

operating system : Windows 11
dotnet version : 6.0.400
QDK : 0.25.228311

[Mathias Soeken]

Qubits need to be released to their 0 state in the same scope they have been allocated. You can try using the MeasureInteger operation on summandLE or reset all qubits explicitly with ResetAll on summand explicitly.

[hofirstb]

Thanks for your reply, I think I see what you mean. However, when I measure the qubits using MultiM, there is no error even though there are qubits in non-zero state and not released. Is it a normal behavior?

[hofirstb]

And ... In the following test case, when using the IncrementByModularInteger operation with increment in [132,765], modulus in [1,4] and the length of target less than 7, there exists a weird memory deallocation issue, even if having reset all qubits to 0 states. But the above range may have some deviation, the following example reports the error on my machine. Maybe it has something to do with the current memory allowance?

Testcase

namespace NISLNameSpace {
	open Microsoft.Quantum.Intrinsic;
	open Microsoft.Quantum.Measurement;
	open Microsoft.Quantum.Arithmetic;
		
	@EntryPoint()
	operation main() : Unit {
		mutable increment = 670;
		mutable modulus = 3;
		use NISLQubitArray38 = Qubit[7];
		mutable target = LittleEndian(NISLQubitArray38);
		IncrementByModularInteger(increment, modulus, target);
		ResetAll(target!);
		ResetAll(NISLQubitArray38);
	}
}