Add new MeasureIfAllZeros operation.

Standard/src/Measurement/Registers.qs

@@ -72,6 +72,29 @@ namespace Microsoft.Quantum.Measurement {
         return ForEach(M, targets);
     }
 
+    /// # Summary
+    /// Measures a register of qubits and returns true if it is in the all-zeros state or false otherwise.
+    ///
+    /// # Description
+    /// Given a register of qubits, checks if that register is in the state
+    /// $\ket{00 \cdots 0}$ by performing a computational basis (i.e.:
+    /// `PauliZ`) measurement on each individual qubit in the register.
+    ///
+    /// # Input
+    /// ## register
+    /// The register of qubits to be measured.
+    ///
+    /// # Output
+    /// `true` if and only if the register is measured to be in the
+    /// $\ket{00 \cdots 0}$ state.
+    ///
+    /// # Remarks
+    /// This operation does not reset its qubits, but projects them to a
+    /// computational basis state.
+    operation MeasureIfAllZeros(register : Qubit[]) : Bool {
+        return All(IsResultZero, ForEach(M, register));
+    }
+
     /// # Summary
     /// Jointly measures a register of qubits in the Pauli Z basis.
     ///

Standard/tests/Measurement/RegisterTests.qs

@@ -0,0 +1,22 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+namespace Microsoft.Quantum.Measurement.Tests {
+    open Microsoft.Quantum.Intrinsic;
+    open Microsoft.Quantum.Canon;
+    open Microsoft.Quantum.Measurement;
+    open Microsoft.Quantum.Diagnostics;
+
+    @Test("QuantumSimulator")
+    operation CheckMeasureIfAllZeros() : Unit {
+        using (qs = Qubit[3]) {
+            Fact(MeasureIfAllZeros(qs), "MeasureIfAllZeros was false for |000⟩ state.");
+
+            X(qs[1]);
+            Fact(not MeasureIfAllZeros(qs), "MeasureIfAllZeros was true for |010⟩ state.");
+
+            ResetAll(qs);
+        }
+    }
+
+}