Fixed #5 bug with classical control

quantastica · Jan 25, 2019 · aa346d0 · aa346d0
1 parent 1acf7d7
commit aa346d0
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Showing 5 changed files with 108 additions and 138 deletions.
diff --git a/dist/quantum-circuit.js b/dist/quantum-circuit.js
diff --git a/dist/quantum-circuit.min.js b/dist/quantum-circuit.min.js
diff --git a/dist/quantum-circuit.min.js.map b/dist/quantum-circuit.min.js.map
diff --git a/lib/quantum-circuit.js b/lib/quantum-circuit.js
@@ -1018,8 +1018,8 @@ QuantumCircuit.prototype.init = function(numQubits) {
 	this.customGates = {};
 	this.cregs = {};
 	this.collapsed = [];
-	this.measureFilter = {};
 	this.prob = [];
+	this.measureResetsQubit = false;
 
 	this.clear();
 };
@@ -1053,7 +1053,6 @@ QuantumCircuit.prototype.resetState = function() {
 
 	// reset measurement
 	this.collapsed = [];
-	this.measureFilter = {};
 	this.prob = [];
 
 	// reset statistics
@@ -1657,6 +1656,32 @@ QuantumCircuit.prototype.applyTransform = function(U, qubits) {
 	this.stateBits = newStateBits;
 };
 
+QuantumCircuit.prototype.resetQubit = function(wire, value) {
+	var U = [
+		[0, 0],
+		[0, 0]
+	];
+
+	var prob = math.complex(0, 0);
+	for(var is in this.state) {
+		var i = parseInt(is);
+		var bit = math.pow(2, (this.numQubits - 1) - wire);
+		if(value ? !!(i & bit) : !(i & bit)) {
+			prob = math.add(prob, this.state[is]);
+		}
+	}
+
+	var mul = 1;
+	if(math.abs(prob)) {
+		mul = math.divide(1, prob);
+	}
+
+	value ? U[1][1] = mul : U[0][0] = mul;
+
+	this.collapsed = [];
+	this.prob = [];
+	this.applyTransform(U, [wire]);
+};
 
 QuantumCircuit.prototype.applyGate = function(gateName, wires, options) {
 	if(gateName == "measure") {
@@ -1666,8 +1691,9 @@ QuantumCircuit.prototype.applyGate = function(gateName, wires, options) {
 
 		var value = this.measure(wires[0], options.creg.name, options.creg.bit);
 
-		// add measure filter
-		this.measureFilter["" + wires[0]] = { value: value };
+		if(this.measureResetsQubit) {
+			this.resetQubit(wires[0], value);
+		}
 
 		return;
 	}
@@ -1685,13 +1711,6 @@ QuantumCircuit.prototype.applyGate = function(gateName, wires, options) {
 	this.prob = [];
 
 	this.applyTransform(rawGate, wires);
-
-	// remove measure filter from affected wires
-	for(var i = 0; i < wires.length; i++) {
-		if(this.measureFilter["" + wires[i]]) {
-			delete this.measureFilter["" + wires[i]];
-		}
-	}
 };
 
 QuantumCircuit.prototype.getRawGate = function(gate, options) {
@@ -2265,17 +2284,7 @@ QuantumCircuit.prototype.exportPyquil = function(comment, decompose, exportAsGat
 	});
 
 	// import MOVE, AND, OR if circuit has conditions
-	var gotConditions = false;
-	for(var column = 0; column < circuit.numCols(); column++) {
-		for(var wire = 0; wire < circuit.numQubits; wire++) {
-			var gate = circuit.getGateAt(column, wire);
-			if(gate && gate.connector == 0) {
-				if(gate.options && gate.options.condition && gate.options.condition.creg) {
-					gotConditions = true;
-				}
-			}
-		}
-	}
+	var gotConditions = circuit.gotClassicalControl();
 	if(gotConditions) {
 		if(importGates) {
 			importGates += ", ";
@@ -2705,18 +2714,7 @@ QuantumCircuit.prototype.exportQuil = function(comment, decompose, exportAsGateN
 		}
 	});
 
-	var gotConditions = false;
-	for(var column = 0; column < circuit.numCols(); column++) {
-		for(var wire = 0; wire < circuit.numQubits; wire++) {
-			var gate = circuit.getGateAt(column, wire);
-			if(gate && gate.connector == 0) {
-				if(gate.options && gate.options.condition && gate.options.condition.creg) {
-					gotConditions = true;
-				}
-			}
-		}
-	}
-
+	var gotConditions = this.gotClassicalControl();
 	var indent = "";
 	if(exportAsGateName) {
 		var params = "";
@@ -3874,6 +3872,8 @@ QuantumCircuit.prototype.partitionCircuit = function(partitionIndex) {
 QuantumCircuit.prototype.run = function(initialValues, options) {
 	options = options || {};
 
+	this.measureResetsQubit = this.gotClassicalControl();
+
 	if(!options.continue) {
 		this.initState();
 		this.stats.duration = 0;
@@ -4077,6 +4077,20 @@ QuantumCircuit.prototype.print = function(onlyPossible) {
 	console.log(this.stateAsString(onlyPossible));
 };
 
+QuantumCircuit.prototype.gotClassicalControl = function() {
+	for(var column = 0; column < this.numCols(); column++) {
+		for(var wire = 0; wire < this.numQubits; wire++) {
+			var gate = this.getGateAt(column, wire);
+			if(gate && gate.connector == 0) {
+				if(gate.options && gate.options.condition && gate.options.condition.creg) {
+					return true;
+				}
+			}
+		}
+	}
+	return false;
+};
+
 QuantumCircuit.prototype.cregsAsString = function() {
 	var s = "";
 	for(var creg in this.cregs) {
@@ -4278,24 +4292,6 @@ QuantumCircuit.prototype.measureAll = function(force) {
 		return this.collapsed;
 	}
 
-	// measure filter ones bit map
-	var onesFilter = 0;
-	for(var sbit in this.measureFilter) {
-		var bit = (this.numQubits - 1) - parseInt(sbit);
-		if(this.measureFilter[sbit].value == 1) {
-			onesFilter += (1 << bit);
-		}
-	}
-
-	// measure filter zeroes bit map
-	var zeroesFilter = 0;
-	for(var sbit in this.measureFilter) {
-		var bit = (this.numQubits - 1) - parseInt(sbit);
-		if(this.measureFilter[sbit].value == 0) {
-			zeroesFilter += (1 << bit);
-		}
-	}
-
 	this.collapsed = [];
 	var randomRange = 0;
 	var maxChance = 0;
@@ -4313,22 +4309,11 @@ QuantumCircuit.prototype.measureAll = function(force) {
 		}
 
 		if(chance > maxChance || (chance == maxChance && (!this.collapsed.length || !Math.floor(Math.random() * (randomRange + 1)) ))) {
-			// filter
 			var i = parseInt(is);
-			var passesFilter = true;
-			if(onesFilter && ((i & onesFilter) != onesFilter)) {
-				passesFilter = false;
-			}
-			if(zeroesFilter && ((~i & zeroesFilter) != zeroesFilter)) {
-				passesFilter = false;
-			}
-
-			if(passesFilter) {
-				maxChance = chance;
-				this.collapsed = [];
-				for(var q = this.numQubits - 1; q >= 0; q--) {
-					this.collapsed.push(1 << q & i ? 1 : 0);
-				}
+			maxChance = chance;
+			this.collapsed = [];
+			for(var q = this.numQubits - 1; q >= 0; q--) {
+				this.collapsed.push(1 << q & i ? 1 : 0);
 			}
 		}
 	}

diff --git a/package.json b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "quantum-circuit",
-  "version": "0.9.51",
+  "version": "0.9.52",
   "description": "Quantum Circuit Simulator",
   "main": "lib/quantum-circuit.js",
   "unpkg": "dist/quantum-circuit.min.js",